0:00:02 > 0:00:06This programme contains scenes which some viewers may find upsetting.
0:00:06 > 0:00:08Contains some scenes of a sexual nature.
0:00:08 > 0:00:10Sex.
0:00:10 > 0:00:15A simple word for the most intimate, sensitive and complex of subjects.
0:00:17 > 0:00:20Sex is at the core of our deepest relationships.
0:00:20 > 0:00:24It's part of what makes us human - it drives our passions,
0:00:24 > 0:00:29our frustrations and our moments of greatest ecstasy.
0:00:30 > 0:00:33One way or another it defines us.
0:00:33 > 0:00:35But unravelling the secrets of sex
0:00:35 > 0:00:39has been a contentious and risky business for science...
0:00:41 > 0:00:44..and an equally big challenge for television.
0:00:48 > 0:00:52For more than 45 years, Horizon and the BBC
0:00:52 > 0:00:57have reported on how science has improved our understanding of sex,
0:00:57 > 0:00:59strived to solve our problems with it,
0:00:59 > 0:01:01and even tried to help us do it better.
0:01:10 > 0:01:13In this programme we'll also look at how science helped us
0:01:13 > 0:01:16understand gender and fertility.
0:01:17 > 0:01:22But can science really save the day when sex goes wrong?
0:01:48 > 0:01:51Biologically, of course, sex is about reproduction,
0:01:51 > 0:01:56but that falls rather short of what it means to us as a species.
0:01:56 > 0:02:00Arousal, desire, sexuality, fertility
0:02:00 > 0:02:04are all incredibly personal to each of us.
0:02:04 > 0:02:06And because of that,
0:02:06 > 0:02:10science got involved in our sex lives rather late in the day.
0:02:10 > 0:02:12Until recently, we knew very little
0:02:12 > 0:02:17about the most basic aspects of human sexuality.
0:02:17 > 0:02:21So how did scientists uncover our sexual secrets
0:02:21 > 0:02:23and what did they learn?
0:02:27 > 0:02:31To truly understand a subject so complex, delicate
0:02:31 > 0:02:34and sometimes plain embarrassing,
0:02:34 > 0:02:37someone needed to ask difficult and intimate questions
0:02:37 > 0:02:41about what we got up to behind closed doors.
0:02:41 > 0:02:43Perhaps the first person to approach sex
0:02:43 > 0:02:47in a systematic and scientific way was Dr Alfred Kinsey.
0:02:49 > 0:02:53Kinsey's lifelong passion was collecting insects.
0:02:53 > 0:02:55But in the 1930s he switched his attention
0:02:55 > 0:02:58to collecting the sexual habits of humans.
0:02:59 > 0:03:03When asked by the bright young students of Indiana University
0:03:03 > 0:03:06to teach a course that covered human sexual behaviour,
0:03:06 > 0:03:10Kinsey discovered that very little research had been carried out
0:03:10 > 0:03:13on the sexual habits of people.
0:03:13 > 0:03:17We knew far more about copulation in other animals than we did in humans.
0:03:20 > 0:03:23I discovered that there is practically nothing known
0:03:23 > 0:03:26about human sexual behaviour
0:03:26 > 0:03:31in comparison with what we knew about the sexual behaviour of other animals
0:03:31 > 0:03:35and in comparison in what we knew about the activities
0:03:35 > 0:03:37of other parts of the human body.
0:03:38 > 0:03:42In order to get meaningful data about the sex lives of humans,
0:03:42 > 0:03:47he asked his own students about their intimate experiences.
0:03:49 > 0:03:52And, for the sake of science, he pulled no punches.
0:03:54 > 0:03:56He asked me questions about the...
0:03:58 > 0:04:01..dimensions of my sex organs which I couldn't answer.
0:04:01 > 0:04:03"Well, take this envelope and this piece of paper,
0:04:03 > 0:04:08"go home and measure yourself and send it to me."
0:04:08 > 0:04:11Kinsey's curiosity became obsession.
0:04:11 > 0:04:15In less than ten years he personally collected
0:04:15 > 0:04:18sexual information on more than 7,000 people.
0:04:18 > 0:04:21Kinsey's results were published in two books
0:04:21 > 0:04:23that both became best sellers.
0:04:23 > 0:04:28Sexual Behaviour in the Human Male appeared in 1948,
0:04:28 > 0:04:32followed by Sexual Behaviour in the Human Female in 1953.
0:04:35 > 0:04:38For the first time, science was attempting to obtain
0:04:38 > 0:04:42objective data on what ordinary people did behind closed doors.
0:04:45 > 0:04:49Don't forget, this was in early days, when there were a lot of suspicions
0:04:49 > 0:04:52about such things, and in addition it was the McCarthy era,
0:04:52 > 0:04:55so Kinsey had to be absolutely circumspect in everything.
0:04:56 > 0:04:59This related to things like dirty jokes, we were never permitted
0:04:59 > 0:05:02to do such things, tell such things, on the staff.
0:05:11 > 0:05:13Kinsey's work revealed that affairs in marriage
0:05:13 > 0:05:16were extremely common for both men and women.
0:05:16 > 0:05:19But that was the least of it.
0:05:19 > 0:05:23His findings showed that even before the sexual revolution of the 1960s,
0:05:23 > 0:05:28nearly 50% of women had premarital sex.
0:05:30 > 0:05:32Amongst 10,000 interviewees,
0:05:32 > 0:05:3892% of men and 65% of women said that they masturbated.
0:05:40 > 0:05:43Just under half of the women interviewed
0:05:43 > 0:05:46reported an erotic experience with another woman.
0:05:51 > 0:05:54And 8% of men and 3% of women
0:05:54 > 0:05:59admitted to some kind of sexual activity with animals.
0:06:03 > 0:06:06It was clear that the laws governing sexual activity in America -
0:06:06 > 0:06:09particularly in the more conservative states -
0:06:09 > 0:06:12were far more restrictive than the reality
0:06:12 > 0:06:15of many Americans' sex lives.
0:06:15 > 0:06:18He told me, with an absolutely straight face,
0:06:18 > 0:06:20perhaps just the trace of a smile,
0:06:20 > 0:06:23that what he knew about the laws of Indiana,
0:06:23 > 0:06:27and what he had learned about the males of Indiana,
0:06:27 > 0:06:30indicated to him that 85% of us should be in jail.
0:06:32 > 0:06:35Kinsey's findings were added to through the decades
0:06:35 > 0:06:37until we had a vivid picture
0:06:37 > 0:06:40of the spectacular variety of human sexual behaviour.
0:06:42 > 0:06:46But scientists didn't just deal with behaviour during sex.
0:06:46 > 0:06:50They were interested in the rules of attraction.
0:06:50 > 0:06:53Males are almost always prepared for sexual behaviour,
0:06:53 > 0:06:56but females usually run away from males,
0:06:56 > 0:06:58and that, after all, creates male interest.
0:07:02 > 0:07:05But when females are receptive they ensure that, whatever happens,
0:07:05 > 0:07:07they're caught.
0:07:09 > 0:07:10At certain times in her cycle,
0:07:10 > 0:07:14the female will allow herself to be caught even more readily.
0:07:14 > 0:07:16The male may appear as a mere toy
0:07:16 > 0:07:18in the hands of a manipulative female,
0:07:18 > 0:07:21but it's probable that each is influenced by hormones.
0:07:22 > 0:07:24More than 30 years on,
0:07:24 > 0:07:28the role of female hormones in influencing sexual desirability
0:07:28 > 0:07:30is still being investigated.
0:07:30 > 0:07:33A group of scientists recently decided
0:07:33 > 0:07:40to conduct a most unusual experiment in a most unusual place.
0:07:40 > 0:07:43They recruited 18 lap dancers
0:07:43 > 0:07:46and asked them to keep detailed records over two months
0:07:46 > 0:07:50of how much they earned every night in tips.
0:07:50 > 0:07:52They also asked the dancers to record data
0:07:52 > 0:07:55about their menstrual cycles.
0:07:55 > 0:07:57Looking at how earnings varied over their monthly cycle,
0:07:57 > 0:08:00they discovered something remarkable.
0:08:02 > 0:08:05During six days around the middle of their monthly cycle,
0:08:05 > 0:08:08when the dancers would have been at their most fertile,
0:08:08 > 0:08:12they were earning an average of around 70 an hour.
0:08:12 > 0:08:16In the rest of the month they earned just 45 an hour.
0:08:18 > 0:08:20If money talks, this suggests
0:08:20 > 0:08:23that male clients found the dancers far more attractive
0:08:23 > 0:08:26when they were at their most fertile.
0:08:26 > 0:08:30The men may have been responding to chemical or physical signals
0:08:30 > 0:08:32that the women were unconsciously producing.
0:08:36 > 0:08:39Understanding what turns us on is one thing,
0:08:39 > 0:08:43but scientists wanted to find out about the physiology of sex.
0:08:44 > 0:08:49In the 1950s, two researchers opened the bedroom door
0:08:49 > 0:08:53in an attempt to quantify exactly what happened to the human body
0:08:53 > 0:08:56before, during and after sex.
0:08:56 > 0:08:58The films they made as part of their research
0:08:58 > 0:09:01still make for uncomfortable viewing.
0:09:01 > 0:09:05In a physiology laboratory, you have to have means...
0:09:05 > 0:09:09create means and measures of evaluating response.
0:09:09 > 0:09:13We needed to know heart rate,
0:09:13 > 0:09:17body temperatures, skin changes...so on.
0:09:17 > 0:09:20And we're the first to say that our work was primitive.
0:09:22 > 0:09:27In 1958, William Masters and Virginia Johnson made this film
0:09:27 > 0:09:31of volunteers in their laboratory having sex
0:09:31 > 0:09:34and becoming sexually aroused through masturbation.
0:09:35 > 0:09:36The areolae begin to swell,
0:09:36 > 0:09:39the entire breast shows increase in size.
0:09:41 > 0:09:44Unsurprisingly, their work was controversial,
0:09:44 > 0:09:47but they made an effort to be as objective as possible
0:09:47 > 0:09:50in the way they collected and reported their findings.
0:09:50 > 0:09:56We did everything to take out the titillation in those early times.
0:09:56 > 0:10:00We kept a very low profile, and yet a very strong one
0:10:00 > 0:10:03within the research and medical, scientific community,
0:10:03 > 0:10:07but they still find it very discomforting
0:10:07 > 0:10:11to think about the means, which is someone in a laboratory,
0:10:11 > 0:10:14someone under lights, someone wired up.
0:10:14 > 0:10:16Even though there's a lot of that going on
0:10:16 > 0:10:19at every other kind of research under the sun...
0:10:19 > 0:10:21when it's sex, it's different.
0:10:21 > 0:10:27From the 1950s onwards, scientists continued to investigate sex,
0:10:27 > 0:10:29building on the work of Masters and Johnson
0:10:29 > 0:10:33and delving even deeper into the physiology of sex.
0:10:33 > 0:10:35And now, with orgasm,
0:10:35 > 0:10:40the involuntary contraction of the outer vaginal ring.
0:10:40 > 0:10:43Laboratory studies led to revelations
0:10:43 > 0:10:46about what happened to the female body during sex.
0:10:46 > 0:10:49The lubrication of the vagina came from its walls
0:10:49 > 0:10:51and not from the cervix as previously thought,
0:10:51 > 0:10:55the important role of the clitoris in female orgasm was confirmed,
0:10:55 > 0:10:57the vagina could contract and expand
0:10:57 > 0:11:01to accommodate a variety of sizes of penis,
0:11:01 > 0:11:06and sexual satisfaction didn't seem to depend on penis size.
0:11:06 > 0:11:09By understanding the physiology of normal sex,
0:11:09 > 0:11:13Masters and Johnson hoped to help those with sexual problems.
0:11:13 > 0:11:16Science was starting to get to grips with sex -
0:11:16 > 0:11:21to understand how our bodies carried out this important function.
0:11:21 > 0:11:23But although their findings were detailed,
0:11:23 > 0:11:26those sexual pioneers lacked the technology
0:11:26 > 0:11:30to get the whole picture of how we made love.
0:11:30 > 0:11:31In particular,
0:11:31 > 0:11:36they couldn't see what was going on inside the human body during sex.
0:11:43 > 0:11:45Reproductive physiologist Dr Roy Levin
0:11:45 > 0:11:49has struggled with the technical limitations of studying sex
0:11:49 > 0:11:50for decades.
0:11:50 > 0:11:52we didn't really have the apparatus
0:11:52 > 0:11:55to allow us to do the measurements, and there was a long period of time
0:11:55 > 0:11:58when you could only guess what was happening
0:11:58 > 0:12:01from the external appearances of men and women in coitus,
0:12:01 > 0:12:03so you couldn't really tell what was happening inside
0:12:03 > 0:12:05because you just can't see.
0:12:06 > 0:12:08Our understanding of sex hasn't moved on much
0:12:08 > 0:12:12since Leonardo da Vinci first started dissecting corpses
0:12:12 > 0:12:16and studying them over 500 years ago.
0:12:16 > 0:12:18The Queen holds this drawing by Leonardo
0:12:18 > 0:12:20in her very own private collection.
0:12:23 > 0:12:28The machine Dr Levin's come to see is this fMRI scanner.
0:12:29 > 0:12:33It's basically a camera which uses magnetic fields
0:12:33 > 0:12:34to penetrate human flesh.
0:12:36 > 0:12:39Today, in the interests of science,
0:12:39 > 0:12:42Michael DeGroot and his girlfriend Liz Leahy
0:12:42 > 0:12:46are going to attempt to have sex in its cramped confines.
0:12:47 > 0:12:48Well, this is the machine.
0:12:48 > 0:12:51As you can see inside it's got, like, two doughnuts,
0:12:51 > 0:12:52those are the very large magnets,
0:12:52 > 0:12:55and in between is the space that you'll lie down in and have coitus.
0:12:55 > 0:12:57So, it's been specially adapted,
0:12:57 > 0:12:59that means just a single board has been put down
0:12:59 > 0:13:01and you'll lay in between the two magnets,
0:13:01 > 0:13:04and hopefully that will capture the images of what's going on
0:13:04 > 0:13:06- during sexual intercourse.- OK.
0:13:06 > 0:13:10Dr Levin is well aware of the problems that need to be overcome
0:13:10 > 0:13:13if this experiment is to be successful.
0:13:13 > 0:13:16It's not the easiest thing in the world to maintain an erection
0:13:16 > 0:13:21and have intercourse in terms of this particular set-up.
0:13:21 > 0:13:24They're brave people that go into these machines.
0:13:24 > 0:13:26I'm interested to see how we're going to manoeuvre ourselves
0:13:26 > 0:13:29in there, because it looks like a pretty constricted space.
0:13:29 > 0:13:33I know they want us in one certain position,
0:13:33 > 0:13:36so I hope that we're able to situate ourselves
0:13:36 > 0:13:38so that they get the images that they want.
0:13:38 > 0:13:40That's my main concern.
0:13:47 > 0:13:50The scanner takes a picture every three seconds
0:13:50 > 0:13:54and produces images of the body from top to bottom.
0:13:55 > 0:13:58This is the first time that such images have been seen
0:13:58 > 0:13:59on British television.
0:14:01 > 0:14:03You can sort of see the penis here,
0:14:03 > 0:14:05that's outside the body from about here,
0:14:05 > 0:14:08and this is the root of the penis inside the body,
0:14:08 > 0:14:11and this is inside the female's body, that's her pubic symphysis,
0:14:11 > 0:14:14the bone, and here would be the pubic hair just around here.
0:14:14 > 0:14:15That's, of course, her bottom
0:14:15 > 0:14:17and this is the vagina that the penis is in,
0:14:17 > 0:14:19and at the top here is the glans.
0:14:19 > 0:14:21And the thing that is obvious in this cross-section
0:14:21 > 0:14:24is the unusual shape of the penis during intercourse.
0:14:24 > 0:14:26Well, it's like a boomerang,
0:14:26 > 0:14:28that's what we've found out by these machines, actually.
0:14:28 > 0:14:31That in fact the penis does look like a boomerang.
0:14:31 > 0:14:34It isn't straight, like they drew it in the early times.
0:14:34 > 0:14:38In fact it is bent, as you can see quite clearly.
0:14:38 > 0:14:39It's actually incredible,
0:14:39 > 0:14:43because as far as when you're having an erection,
0:14:43 > 0:14:48you think it's as hard and solid as...rock or wood or something,
0:14:48 > 0:14:50but when you look at those pictures it's unbelievable,
0:14:50 > 0:14:51you have the 90-degree angle,
0:14:51 > 0:14:54and you can't even imagine that it would bend that way.
0:14:54 > 0:14:56It's really fascinating to see what the body does.
0:14:58 > 0:15:00Nobody knows why the penis has to go through
0:15:00 > 0:15:03such extraordinary contortions.
0:15:03 > 0:15:05One theory is that it's a relic from our past,
0:15:05 > 0:15:10when sex was more commonly done on all fours, and not face to face.
0:15:22 > 0:15:25Understanding the mechanics of sex and desire
0:15:25 > 0:15:29gave scientists the knowledge they needed to move to the next stage,
0:15:29 > 0:15:32of trying to fix our many sexual problems.
0:15:32 > 0:15:37Male impotence seemed to be one of the most obvious issues to tackle.
0:15:37 > 0:15:41But the first idea of how to fix erectile dysfunction
0:15:41 > 0:15:45wouldn't come from a scientific laboratory.
0:15:54 > 0:15:58Instead, the breakthrough came from a man named Geddings Osbon.
0:15:58 > 0:16:01He ran a tyre retreading company,
0:16:01 > 0:16:05but he became one of history's most unexpected medical innovators
0:16:05 > 0:16:09when he came up with a very practical mechanical solution
0:16:09 > 0:16:11for his own impotence.
0:16:12 > 0:16:16The only thing he knew about was maybe taking a small pump.
0:16:16 > 0:16:20At this time he got a regular bicycle pump.
0:16:22 > 0:16:28This tube is tubing that was used on the windshield wipers of cars.
0:16:31 > 0:16:36This metal valve is the kind of metal valve you find on truck tyres.
0:16:38 > 0:16:40He reversed the cylinder in here,
0:16:40 > 0:16:42to make it to where...
0:16:42 > 0:16:46when he pulled up, it created negative pressure.
0:16:46 > 0:16:52So he found that if he could take this tube here and connect it,
0:16:52 > 0:16:56that he could pull the air out of the cylinder,
0:16:56 > 0:17:00so then he would place this against his body and he would pull up
0:17:00 > 0:17:03and it would pull blood into the penis,
0:17:03 > 0:17:06and then in the cylinder he would get an erection.
0:17:06 > 0:17:10Geddings Osbon's invention achieved mechanically
0:17:10 > 0:17:12what the body normally does itself -
0:17:12 > 0:17:15drawing blood into the spongy erectile tissue
0:17:15 > 0:17:18which runs the length of the penis.
0:17:18 > 0:17:20When an erection happens naturally,
0:17:20 > 0:17:24the rising pressure inside the penis closes down the veins
0:17:24 > 0:17:27to stop blood leaving and maintain the erection.
0:17:27 > 0:17:31Osbon used an elastic band.
0:17:31 > 0:17:34His system was reluctantly adopted by the medical community
0:17:34 > 0:17:36in the 1980s.
0:17:36 > 0:17:41For years, the vacuum erection pump was the only mainstream solution
0:17:41 > 0:17:43to a very common problem.
0:17:43 > 0:17:46But it's easy to understand that Osbon's invention
0:17:46 > 0:17:49didn't suit every man suffering from impotence.
0:17:49 > 0:17:52What was needed was something more convenient,
0:17:52 > 0:17:55that didn't ruin the moment.
0:17:58 > 0:18:01The solution came in the form of a chemical compound
0:18:01 > 0:18:04developed in the late '90s.
0:18:08 > 0:18:11Scientists at Pfizer were looking for a new drug for angina,
0:18:11 > 0:18:15something that would relax the blood vessels around the heart.
0:18:17 > 0:18:20After screening hundreds of thousands of compounds,
0:18:20 > 0:18:25they ended up with UK-92,480.
0:18:25 > 0:18:27But its trials in humans were a letdown.
0:18:27 > 0:18:30It was about to be consigned back to the stores
0:18:30 > 0:18:35when the triallists came back reporting an unusual side effect -
0:18:35 > 0:18:36lots of erections.
0:18:38 > 0:18:41Add the drug, and the relaxations get larger.
0:18:41 > 0:18:44But it's... The trace's upside down.
0:18:44 > 0:18:47By making a crude mock-up of the human sexual apparatus,
0:18:47 > 0:18:52senior scientist Chris Wayman found an ingenious way
0:18:52 > 0:18:54to test this anecdotal evidence.
0:18:57 > 0:18:59These are actually penile blood vessels
0:18:59 > 0:19:02that we have in a tissue bath.
0:19:03 > 0:19:07Think of this as the brain, this is the brain and the spinal cord.
0:19:07 > 0:19:10When you become aroused, your brain switches on.
0:19:10 > 0:19:11We can mimic this
0:19:11 > 0:19:17by switching on the equivalent of the central nervous system in the brain.
0:19:17 > 0:19:22It sends electricity down to the tissue baths and across the tissues.
0:19:22 > 0:19:24And when we pass an electric current
0:19:24 > 0:19:27across these small pieces of penile tissue, they relax,
0:19:27 > 0:19:31and ultimately that's what happens during penile erection.
0:19:33 > 0:19:37Relaxed penile blood vessels mean more blood flow to the penis,
0:19:37 > 0:19:40and so an erection.
0:19:40 > 0:19:44What Chris did was take penile blood vessels from impotent men,
0:19:44 > 0:19:47vessels that didn't respond when he flipped the brain-switch,
0:19:47 > 0:19:51and then added UK-92,480 to the tissue bath.
0:19:52 > 0:19:55What was most amazing about this study
0:19:55 > 0:19:58was that we saw a restoration of erectile response.
0:19:59 > 0:20:02It's very rare in any tissue preparation
0:20:02 > 0:20:06to convert dysfunctional to normal function.
0:20:06 > 0:20:10So now we were onto something that can only be described as special.
0:20:13 > 0:20:19UK-92,480 was renamed Viagra.
0:20:19 > 0:20:21And within weeks of going on sale,
0:20:21 > 0:20:25tens of thousands of prescriptions were being written every day.
0:20:28 > 0:20:30You would never have been able to predict
0:20:30 > 0:20:33that this was going to have beneficial effects
0:20:33 > 0:20:36on millions and millions of men throughout the world.
0:20:36 > 0:20:41A little bit of science having an effect of self-esteem, anxiety,
0:20:41 > 0:20:45depression levels and ultimately creating enhanced relationships.
0:21:12 > 0:21:16Today, Viagra is one of the most widely prescribed drugs
0:21:16 > 0:21:20in the world, with about six tablets being dispensed every second.
0:21:20 > 0:21:22By fumbling in the dark,
0:21:22 > 0:21:27science had fixed a problem that had plagued men for centuries.
0:21:29 > 0:21:31But there are bigger and deadlier problems
0:21:31 > 0:21:33when it comes to sex,
0:21:33 > 0:21:36and some of them would prove much more resistant
0:21:36 > 0:21:38to scientific solutions.
0:21:44 > 0:21:49Sex brings bodies into intimate physical contact with each other.
0:21:49 > 0:21:53But it also allows sexually transmitted diseases to travel
0:21:53 > 0:21:55from one person to another.
0:21:57 > 0:22:02But by the 1970s many of these diseases were under control -
0:22:02 > 0:22:04in the developed world at least.
0:22:06 > 0:22:12Then, in the early 1980s, along came a terrifying new sexual infection.
0:22:12 > 0:22:16Horizon broadcast one of the first documentaries
0:22:16 > 0:22:18about this terrible new disease.
0:22:19 > 0:22:22The first troubling signs were noticed
0:22:22 > 0:22:24in the homosexual communities of America,
0:22:24 > 0:22:28in particular in New York's Greenwich Village.
0:22:29 > 0:22:32Gay men were contracting bizarre infections
0:22:32 > 0:22:35that seldom infected healthy people.
0:22:35 > 0:22:40Toxoplasmosis, Pneumocystis carinii pneumonia,
0:22:40 > 0:22:44Cryptosporidiosis, and types of tuberculosis
0:22:44 > 0:22:49that normally only infected birds were killing men in their prime.
0:22:49 > 0:22:52Then the disease was noticed in intravenous drug users,
0:22:52 > 0:22:57many of who were in prison by the time they started having symptoms.
0:22:57 > 0:23:00Prisoner Castranova's speech is affected.
0:23:00 > 0:23:02He may have Toxoplasmosis
0:23:02 > 0:23:03as well as the pneumonia.
0:23:03 > 0:23:05This is one of his better days.
0:23:05 > 0:23:07What's rough now is,
0:23:07 > 0:23:10I don't know if I'll ever see my kids again.
0:23:10 > 0:23:13Scientists were horrified when they looked at blood
0:23:13 > 0:23:15taken from these patients.
0:23:15 > 0:23:18The numbers of a particular white blood cell,
0:23:18 > 0:23:22known as a T helper cell, were at rock bottom.
0:23:22 > 0:23:25Without this vital cornerstone of the immune system,
0:23:25 > 0:23:29infections which would normally be easily fended off
0:23:29 > 0:23:31could become lethal.
0:23:31 > 0:23:34Finally, behind all these odd infections,
0:23:34 > 0:23:37scientists discovered a puppet master.
0:23:37 > 0:23:39Something that was weakening the immune system,
0:23:39 > 0:23:43allowing other, usually mild, infections to wreak havoc.
0:23:44 > 0:23:46They tracked down the cause
0:23:46 > 0:23:51of what had become known as acquired immunodeficiency syndrome - AIDS.
0:23:52 > 0:23:56It was a virus - HIV.
0:23:59 > 0:24:01Like a walking time bomb.
0:24:02 > 0:24:04You know?
0:24:04 > 0:24:05That's what they said.
0:24:06 > 0:24:10"You're like a walking time bomb."
0:24:10 > 0:24:12He died soon after.
0:24:12 > 0:24:15And Mrs Castranova also died.
0:24:15 > 0:24:18She was incubating AIDS while her husband was in prison.
0:24:20 > 0:24:24Since HIV was first identified,
0:24:24 > 0:24:27over 60 million people have become infected worldwide.
0:24:28 > 0:24:34Of those who contracted the virus, AIDS has killed 30 million people.
0:24:35 > 0:24:39It's one of the worst pandemics the world has ever known.
0:24:40 > 0:24:45In the intervening years, science has scrambled to find drugs
0:24:45 > 0:24:48that could cure the disease, with only limited success.
0:24:54 > 0:24:56COCKEREL CROWS
0:24:58 > 0:25:01But then something surprising was noticed
0:25:01 > 0:25:03in a valley in Central Africa.
0:25:03 > 0:25:06Something which would suggest an effective way
0:25:06 > 0:25:08of combating the disease.
0:25:15 > 0:25:19On one side of the valley people are dying of AIDS in their hundreds,
0:25:19 > 0:25:22while their neighbours, with the same apparent behaviour and risk,
0:25:22 > 0:25:25are far less affected by the disease.
0:25:25 > 0:25:29MAN SPEAKS IN OWN LANGUAGE
0:25:29 > 0:25:33In this school, if the epidemic continues to spread,
0:25:33 > 0:25:3760% of these children will die from AIDS.
0:25:43 > 0:25:45But the extraordinary thing is
0:25:45 > 0:25:47that if they were children just a mile away
0:25:47 > 0:25:49on the other side of this valley,
0:25:49 > 0:25:53their chances of dying would be three times less.
0:25:59 > 0:26:01Scientists realised the only difference
0:26:01 > 0:26:05between the AIDS-free side of the valley and the other
0:26:05 > 0:26:07was that the boys on the healthy side
0:26:07 > 0:26:11had been circumcised, according to local custom.
0:26:11 > 0:26:15Removing the foreskin seemed to have an almost miraculous effect
0:26:15 > 0:26:18in preventing the men from getting infected.
0:26:21 > 0:26:22Intrigued by the idea,
0:26:22 > 0:26:25anthropologist Priscilla Reining compiled data
0:26:25 > 0:26:29on hundreds of circumcised and uncircumcised tribes.
0:26:30 > 0:26:34When this data was matched up with a map of HIV prevalence,
0:26:34 > 0:26:37the correlation was startling.
0:26:37 > 0:26:39This was the map which we published,
0:26:39 > 0:26:46and the black are depicting ethnic groups
0:26:46 > 0:26:51which do not practice circumcision as a norm, and the grey
0:26:51 > 0:26:55are groups which do practice circumcision.
0:26:55 > 0:26:59So this is a corridor which runs from the southern Sudan
0:26:59 > 0:27:01down into South Africa.
0:27:02 > 0:27:07Here is an overlay of HIV.
0:27:07 > 0:27:11And you can see that there's a high degree of conformity
0:27:11 > 0:27:17between the red, which is relatively high HIV rates.
0:27:17 > 0:27:23There is red down the same band, and...
0:27:26 > 0:27:28..interestingly, over here as well.
0:27:31 > 0:27:33The statistical...
0:27:33 > 0:27:39statistical relationship was .90, which is very good.
0:27:39 > 0:27:42And so, you know, wow, it really is there.
0:27:47 > 0:27:48But why should circumcision
0:27:48 > 0:27:52so drastically cut the risk of HIV infection?
0:27:53 > 0:27:56The answer lay in particular cells of the immune system
0:27:56 > 0:27:58present in the foreskin.
0:27:58 > 0:28:01Cells which HIV was targeting.
0:28:09 > 0:28:13The green cells are Langerhans cells.
0:28:13 > 0:28:16They're in the front line of the body's battle against infection.
0:28:16 > 0:28:20They capture infectious agents like viruses
0:28:20 > 0:28:22and show them to other cells of the immune system,
0:28:22 > 0:28:25which can actively fight the infection.
0:28:28 > 0:28:33But HIV uses the Langerhans cells as a gateway to the body.
0:28:37 > 0:28:39It's a Trojan horse, basically.
0:28:39 > 0:28:45The Langerhans cell is in fact allowing the virus to enter the body,
0:28:45 > 0:28:49and carry to the very system, namely the lymph glands,
0:28:49 > 0:28:52where those viruses can start proliferating.
0:29:04 > 0:29:09Circumcision reduces the risk of being infected by HIV by over 60%,
0:29:09 > 0:29:13and is now recommended by the World Health Organisation
0:29:13 > 0:29:15as an important part of disease prevention.
0:29:18 > 0:29:22It's hoped that HIV/ AIDS will be vanquished one day,
0:29:22 > 0:29:25but for the moment the disease is being held at bay
0:29:25 > 0:29:29by a mixture of anti-retroviral drugs and sex education.
0:29:37 > 0:29:39As well as tackling diseases that spread amongst us
0:29:39 > 0:29:41through sexual contact,
0:29:41 > 0:29:46scientists have also tried to help with problems of gender identity.
0:29:47 > 0:29:50Biologically speaking, it should be straightforward.
0:29:50 > 0:29:55After all, the chromosomes we get from our parents determine our sex.
0:29:55 > 0:30:01Two X chromosomes for a girl, an X and a Y chromosome for a boy.
0:30:04 > 0:30:08Beyond that simple equation, though, scientists are still studying
0:30:08 > 0:30:13how exactly our genes turn us into either men or women.
0:30:23 > 0:30:26Of course, there's much more to being female or male
0:30:26 > 0:30:30than just which body parts you do or don't have.
0:30:30 > 0:30:34What makes us feel and act like men or women?
0:30:34 > 0:30:38There has been a long debate over how much our gender identity
0:30:38 > 0:30:42is controlled by nature or nurture.
0:30:42 > 0:30:44And for the latter half of the 20th century,
0:30:44 > 0:30:49the argument focused on the tragic story of one boy.
0:30:54 > 0:31:00On 27th April 1966, Janet Reimer took her baby twin boys
0:31:00 > 0:31:04Bruce and Brian to her local hospital in Winnipeg, Canada,
0:31:04 > 0:31:06for a routine circumcision.
0:31:08 > 0:31:10But instead of using a knife,
0:31:10 > 0:31:14doctors chose to use an electric cauterisation technique.
0:31:14 > 0:31:18Bruce went first, but the equipment malfunctioned,
0:31:18 > 0:31:21and Bruce's penis was burned beyond repair.
0:31:24 > 0:31:26Janet was devastated.
0:31:27 > 0:31:30Daily, I was crying.
0:31:30 > 0:31:32Every time I changed his diaper I'd cry.
0:31:33 > 0:31:35I was in shock...
0:31:36 > 0:31:38..for a while.
0:31:39 > 0:31:43I guess about a year I was in shock.
0:31:44 > 0:31:49Janet had no idea what to do after the botched operation.
0:31:49 > 0:31:52Until, one night, she saw a glimmer of hope
0:31:52 > 0:31:54when she was watching a talk show.
0:31:55 > 0:32:01One of the guests was a radical psychologist called Dr John Money.
0:32:01 > 0:32:04Dr John Money, a psychologist at John Hopkins,
0:32:04 > 0:32:07is one of the leading advocates of sex-change operations.
0:32:07 > 0:32:11Dr Money is in the bear pit tonight with Alvin Davis.
0:32:11 > 0:32:16Dr Money, it's still a pretty drastic procedure, isn't it?
0:32:16 > 0:32:22Well, it's a drastic procedure by your standards and mine,
0:32:22 > 0:32:24but for the people who are living in desperation,
0:32:24 > 0:32:27perhaps the best way to understand it
0:32:27 > 0:32:31is that it seems no more drastic to them than circumcision.
0:32:34 > 0:32:37Hoping that something could be done for her son,
0:32:37 > 0:32:39Janet wrote to Dr Money.
0:32:39 > 0:32:42He called back as soon as he got her letter.
0:32:44 > 0:32:48Dr Money needed Bruce's unique case to prove a theory
0:32:48 > 0:32:50he had been working on.
0:32:50 > 0:32:54His theory was that gender wasn't just down to genes -
0:32:54 > 0:32:56that it was much more malleable.
0:32:57 > 0:33:01He believed that you could take a child who was genetically one sex
0:33:01 > 0:33:04and raise it successfully as the other -
0:33:04 > 0:33:07provided you started in infancy.
0:33:07 > 0:33:10His theory was known as Gender Neutrality.
0:33:14 > 0:33:17Faced with an almost impossible decision,
0:33:17 > 0:33:22on Dr Money's advice, Janet had her two-year-old son castrated.
0:33:22 > 0:33:27From then on he was dressed and raised as a girl, called Brenda.
0:33:27 > 0:33:31When Dr Money announced his work with the Reimers to the world,
0:33:31 > 0:33:33he was hailed as a genius.
0:33:36 > 0:33:40His theory on the malleability of gender became hugely influential
0:33:40 > 0:33:44amongst doctors and psychologists around the world.
0:33:44 > 0:33:46But there was a problem.
0:33:46 > 0:33:48Unbeknownst to the scientific community,
0:33:48 > 0:33:51the experiment had gone wrong.
0:34:08 > 0:34:10I didn't like dressing like a girl,
0:34:10 > 0:34:11I didn't like behaving like a girl,
0:34:11 > 0:34:13I didn't like acting like a girl.
0:34:15 > 0:34:19Brenda Reimer was now living as a man called David.
0:34:22 > 0:34:27After the operation, Brenda had been taught to dress and act like a girl.
0:34:27 > 0:34:30But she felt like a boy.
0:34:31 > 0:34:33Well, I wore dresses on occasion.
0:34:35 > 0:34:38And I never played with girl's stuff,
0:34:38 > 0:34:41I usually got stuck with dolls or something like that,
0:34:41 > 0:34:44for my birthday or Christmas.
0:34:44 > 0:34:46They sat in a corner collecting dust.
0:34:46 > 0:34:48I played with my brother's things.
0:34:53 > 0:34:57During the early years, I thought we had made the right choice -
0:34:57 > 0:35:01that it would work out. Dr Money kept saying it would work out.
0:35:01 > 0:35:05And I thought, well, he should know.
0:35:09 > 0:35:13But when Brenda was 14, her parents, realising the confusion and misery
0:35:13 > 0:35:19caused by her changed identity, told her and her brother the truth.
0:35:19 > 0:35:23You don't wake up one morning and say, "Oh, I'm a boy today."
0:35:23 > 0:35:25You know? You know!
0:35:25 > 0:35:29It's in you! You know, it's in your genetics, it's in your brain.
0:35:29 > 0:35:31Nobody has to tell you who you are.
0:35:32 > 0:35:38Dr Money's experiment to raise a boy as a girl had failed,
0:35:38 > 0:35:41and the story of the Reimer brothers ended with tragedy.
0:35:44 > 0:35:47Unable to deal with what had happened to David,
0:35:47 > 0:35:51his brother Brian became depressed and died from a drug overdose.
0:35:53 > 0:35:55Traumatised by his brother's death,
0:35:55 > 0:35:58and with a catalogue of personal disasters in his adult life,
0:35:58 > 0:36:02in 2004, David shot himself.
0:36:03 > 0:36:05It didn't work because that's life.
0:36:05 > 0:36:08Because you're human, and you're not stupid,
0:36:08 > 0:36:12and eventually... you'll end up being who you are.
0:36:26 > 0:36:29The tragic story of David Reimer seems to show that
0:36:29 > 0:36:34the roots of our gender identity lie in genetics and not in nurture.
0:36:34 > 0:36:38And indeed evidence that Dr Money's theory might have been flawed
0:36:38 > 0:36:41was already emerging in the late 1960s,
0:36:41 > 0:36:45just as he was announcing his supposedly successful theory.
0:36:45 > 0:36:50That evidence came from the brain of a rat in Los Angeles.
0:36:55 > 0:36:57A team from the University of California
0:36:57 > 0:37:00were comparing male and female rat brains
0:37:00 > 0:37:02in minute detail.
0:37:04 > 0:37:06They were hoping to find a physical difference
0:37:06 > 0:37:11that would explain differences in male and female behaviour.
0:37:13 > 0:37:16Slice by slice, millimetre by millimetre,
0:37:16 > 0:37:18they mapped the tiny organs.
0:37:22 > 0:37:25And one day, they found something.
0:37:28 > 0:37:30Comparing tissue from the hypothalamus,
0:37:30 > 0:37:32right in the centre of the brain,
0:37:32 > 0:37:36they noticed a structural difference between the sexes.
0:37:39 > 0:37:43A discrete part of the hypothalamus was twice as big
0:37:43 > 0:37:46in the male rat's brain, on the left,
0:37:46 > 0:37:49as in the female's, on the right.
0:37:54 > 0:37:59Here's that part, isolated from the brain of a male rat.
0:37:59 > 0:38:03They called it the sexually dimorphic nucleus, or SDN.
0:38:03 > 0:38:06And here it is in the female rat's brain.
0:38:11 > 0:38:13Here was a clear anatomical difference
0:38:13 > 0:38:17between the brains of male and female rats.
0:38:18 > 0:38:23These differences are created by sex hormones before the rat is born.
0:38:23 > 0:38:25While a male rat is in the womb,
0:38:25 > 0:38:28testosterone is already shaping its brain.
0:38:30 > 0:38:34The SDN is also larger in the human male brain,
0:38:34 > 0:38:36compared with the female.
0:38:38 > 0:38:41And the SDN is involved in sexual behaviour.
0:38:43 > 0:38:46The discovery of the SDN was important because it showed
0:38:46 > 0:38:50that there were real differences in the brains of men and women.
0:38:51 > 0:38:55And other real-life cases showed that gender identity
0:38:55 > 0:38:58was already permanently programmed at birth.
0:39:01 > 0:39:05Dr Money's experiment was ultimately flawed, because of
0:39:05 > 0:39:09the way that hormones affected the fledgling brain of the baby.
0:39:12 > 0:39:16But while gender identity is fixed at birth for most people,
0:39:16 > 0:39:20for others, it's much less cut-and-dried.
0:39:22 > 0:39:26If called upon, science sometimes has a solution.
0:39:29 > 0:39:34Max Toft, a software engineer, is physically and genetically a woman.
0:39:34 > 0:39:36But she wants to be a man.
0:39:38 > 0:39:41I remembered having this distinct moment where I thought
0:39:41 > 0:39:44that God had made a mistake and that I should have been a boy -
0:39:44 > 0:39:47which was interesting, because I grew up in an atheist household!
0:39:48 > 0:39:50To make her body more male,
0:39:50 > 0:39:54Max is going to undergo a course of testosterone.
0:39:54 > 0:39:56Dr Ruben Gur, one of the leading scientists
0:39:56 > 0:39:58on how hormones affect the brain,
0:39:58 > 0:40:02is going to put Max though a series of physical and psychological tests
0:40:02 > 0:40:05before and after her treatment.
0:40:08 > 0:40:09Go.
0:40:12 > 0:40:16UPBEAT MUSIC PLAYS
0:40:25 > 0:40:27Stop.
0:40:27 > 0:40:32Max shows a fairly typical female, erm,
0:40:32 > 0:40:35profile, cognitively.
0:40:35 > 0:40:41Erm, and, er, I'd be curious to see whether there is a change in that.
0:40:43 > 0:40:46After six months of testosterone therapy,
0:40:46 > 0:40:49the most obvious changes are to Max's body -
0:40:49 > 0:40:53his voice is deeper, and he's got more body hair.
0:41:01 > 0:41:04But it's the psychological and practical tests Max underwent
0:41:04 > 0:41:08before and after hormone treatment which have been the most startling.
0:41:12 > 0:41:15What we are seeing, really, is, er,
0:41:15 > 0:41:19is a female brain turning into a male brain. It was quite, er,
0:41:19 > 0:41:22quite amazing to see it on a single individual.
0:41:23 > 0:41:26This is a scan of Max's brain when he was a woman.
0:41:26 > 0:41:30The red areas show the parts of the brain he used
0:41:30 > 0:41:32when trying to read emotions.
0:41:32 > 0:41:37And this is a scan of Max's brain doing the same task but as a man.
0:41:37 > 0:41:41The more red in the scan picture, the harder the brain is working.
0:41:41 > 0:41:44And as you can see, it seems that he found it much easier
0:41:44 > 0:41:47to read emotions when he was a woman than he does now.
0:41:48 > 0:41:51In his case, the second time, he had
0:41:51 > 0:41:55more difficulties with the task, he had to put in more effort
0:41:55 > 0:41:59in order to perform that particular...that particular task.
0:41:59 > 0:42:03So, he's... His brain responds more like a male brain
0:42:03 > 0:42:06to the task of trying to distinguish the emotions.
0:42:12 > 0:42:16But how did Max do in the practical tests?
0:42:20 > 0:42:24All the changes are in the direction that we expected,
0:42:24 > 0:42:27in terms of becoming more masculine.
0:42:27 > 0:42:30- Interesting.- Er, so, remember the finger-tapping?
0:42:30 > 0:42:35- Uh-huh.- You managed to squeeze in another three taps
0:42:35 > 0:42:37- per minute.- Whoo-hoo!
0:42:37 > 0:42:41His spatial awareness has also dramatically improved.
0:42:41 > 0:42:44Last time, you did 75 correct.
0:42:44 > 0:42:46This time, you did 118 correct.
0:42:46 > 0:42:49- Right.- That's pretty much the end of the good news...- Right.
0:42:49 > 0:42:53..because, er, with becoming a male,
0:42:53 > 0:42:55erm, you also lost a little bit.
0:42:56 > 0:42:59Max's visual memory has deteriorated,
0:42:59 > 0:43:01and he's not as good with words.
0:43:01 > 0:43:04I was actually surprised. I didn't...
0:43:04 > 0:43:08I was thinking maybe one or two...
0:43:08 > 0:43:11tests would change, and, er...
0:43:11 > 0:43:15Erm, this is after all a fairly brief period of time.
0:43:15 > 0:43:18You would expect changes on those tests
0:43:18 > 0:43:21to take place over a longer period.
0:43:24 > 0:43:25Max is still sceptical
0:43:25 > 0:43:29about the extent to which testosterone has changed his brain.
0:43:29 > 0:43:33But he acknowledges it has affected how he feels.
0:43:33 > 0:43:38My body is changing, and it has been surprising to go through that.
0:43:38 > 0:43:42It's been kind of exciting, and there were changes that I wasn't...
0:43:42 > 0:43:44that I didn't expect to go through. There was a period of time
0:43:44 > 0:43:46where I had a really hard time crying,
0:43:46 > 0:43:49and it felt biological to me.
0:43:49 > 0:43:52There was something biochemical preventing me from doing it.
0:43:52 > 0:43:55Like, it really felt like a big block,
0:43:55 > 0:43:58and that was kind of a scary moment for me.
0:44:01 > 0:44:05For most people, the biggest impact that science has had on
0:44:05 > 0:44:09our sex lives has been in giving us greater control over reproduction.
0:44:12 > 0:44:15Thanks to medical advances over recent decades,
0:44:15 > 0:44:19today, more healthy babies are born than ever before.
0:44:24 > 0:44:26And the invention of the contraceptive pill
0:44:26 > 0:44:29gave women the power to decide when they have them.
0:44:36 > 0:44:39As pills go, THE Pill is a particularly tiny one,
0:44:39 > 0:44:43and yet its effect on the sex lives of women
0:44:43 > 0:44:45has been monumental.
0:44:45 > 0:44:49But behind this little piece of sexual liberation
0:44:49 > 0:44:51is the story of an intrepid scientist
0:44:51 > 0:44:55who went to the ends of the earth, and then disappeared.
0:45:01 > 0:45:04In order to make a contraceptive pill for women,
0:45:04 > 0:45:08scientists needed a source of the sex hormone progesterone.
0:45:08 > 0:45:11But in the early part of the last century,
0:45:11 > 0:45:14producing these hormones in a laboratory
0:45:14 > 0:45:17was difficult, and phenomenally expensive.
0:45:19 > 0:45:23But Professor Russell Marker, of Pennsylvania State University,
0:45:23 > 0:45:25had an idea.
0:45:25 > 0:45:27He knew that some animal hormones
0:45:27 > 0:45:30were very similar to chemicals in plants,
0:45:30 > 0:45:33and he identified a raw botanic ingredient
0:45:33 > 0:45:37that theoretically could be used to produce progesterone.
0:45:42 > 0:45:44Using the roots of a yucca plant
0:45:44 > 0:45:47he found in the south-western United States,
0:45:47 > 0:45:49he proved his chemical principle.
0:45:49 > 0:45:53However, this plant didn't naturally produce enough of the raw material
0:45:53 > 0:45:55to ever be economically viable.
0:45:57 > 0:46:01Then, in November 1941, Marker found what he was looking for.
0:46:01 > 0:46:06In an old botany textbook, he saw a rare type of wild yam
0:46:06 > 0:46:12with an enormous root system that was said to weigh almost 100 kilos.
0:46:12 > 0:46:14But there was a problem -
0:46:14 > 0:46:19the yam only grew in an isolated region of the Mexican jungle.
0:46:24 > 0:46:27The intrepid Marker travelled there alone
0:46:27 > 0:46:30and smuggled two huge roots of this rare plant
0:46:30 > 0:46:33back to the United States.
0:46:36 > 0:46:41Once home, he successfully synthesised 2kg of progesterone -
0:46:41 > 0:46:44far more than anyone had ever seen before.
0:46:45 > 0:46:47Marker wanted to go into business,
0:46:47 > 0:46:50but he was shunned by the major pharmaceutical companies,
0:46:50 > 0:46:53so he founded his own, called Syntex,
0:46:53 > 0:46:56and began to produce more progesterone.
0:46:59 > 0:47:02But in 1949, with business about to boom,
0:47:02 > 0:47:05Marker mysteriously vanished.
0:47:07 > 0:47:10His work would lay the foundations
0:47:10 > 0:47:14for the production of the modern contraceptive pill in the 1960s.
0:47:14 > 0:47:17But Marker himself was still nowhere to be found.
0:47:17 > 0:47:22It was rumoured that he'd died in a mental institution in Mexico.
0:47:25 > 0:47:31But in 1977, Horizon tracked down the elusive professor.
0:47:31 > 0:47:35He was living just a few miles away from Penn State University,
0:47:35 > 0:47:38where he first made his remarkable discovery.
0:47:38 > 0:47:42In this interview from the time, it's not difficult to see
0:47:42 > 0:47:46why Marker had become so disillusioned with big business.
0:47:46 > 0:47:47At the end of the year,
0:47:47 > 0:47:49when I thought the profits should be distributed...
0:47:49 > 0:47:52I knew that there were very nice profits,
0:47:52 > 0:47:54including the profit that was obtained
0:47:54 > 0:47:58from the first 2kg of progesterone that I had made.
0:47:58 > 0:48:02And I had made 25 or 30kg during the year
0:48:02 > 0:48:08of progesterone - it was selling for over 25 a gram
0:48:08 > 0:48:10at that time.
0:48:10 > 0:48:13I went to the senior partner in the firm
0:48:13 > 0:48:17and asked him about the profits, and he said there were no profits.
0:48:17 > 0:48:20And he eventually told me that, er,
0:48:20 > 0:48:22he had taken the profits as salary,
0:48:22 > 0:48:24and there was nothing I could do about it.
0:48:24 > 0:48:26So I walked out of Syntex.
0:48:39 > 0:48:44The Pill gave women the power to prevent unwanted pregnancies.
0:48:44 > 0:48:46But for couples who want children,
0:48:46 > 0:48:49becoming pregnant can sometimes be difficult.
0:48:49 > 0:48:52Many problems can interfere with conception,
0:48:52 > 0:48:55causing anguish for parents.
0:48:57 > 0:49:01It was once thought that being able to control this natural process
0:49:01 > 0:49:02would be impossible.
0:49:02 > 0:49:07Then, in 1978, a baby was born using a radical new technique
0:49:07 > 0:49:11that has revolutionised the treatment of infertility.
0:49:14 > 0:49:17Researchers removed eggs from the mother
0:49:17 > 0:49:21and combined them with sperm from the father in a Petri dish.
0:49:22 > 0:49:24The embryologists could then check
0:49:24 > 0:49:26to see if the embryo's development was proceeding normally
0:49:26 > 0:49:30before re-implanting only the most healthy embryos
0:49:30 > 0:49:33back into the mother, for nature to take its course.
0:49:36 > 0:49:40The technical name for the procedure is in vitro fertilisation,
0:49:40 > 0:49:42or IVF.
0:49:42 > 0:49:46The media coined the phrase "test-tube babies".
0:49:47 > 0:49:50At the time, it was highly controversial.
0:49:52 > 0:49:56Since those early days, hundreds of thousands of healthy babies
0:49:56 > 0:49:59have started their lives in this way,
0:49:59 > 0:50:01and the stigma has gone.
0:50:01 > 0:50:04It's one of science's greatest success stories.
0:50:08 > 0:50:12But the moral dilemmas thrown up by test-tube babies didn't vanish.
0:50:12 > 0:50:14People began to worry that
0:50:14 > 0:50:16the technique gave scientists the opportunity
0:50:16 > 0:50:21to do far more than simply helping infertile couples have babies.
0:50:23 > 0:50:25IVF meant that it one day might be possible
0:50:25 > 0:50:28to tamper with the DNA of an embryo in the lab
0:50:28 > 0:50:31and create a bespoke baby.
0:50:35 > 0:50:3830 years ago, Horizon made a drama
0:50:38 > 0:50:41where families were no longer prepared to leave the appearance
0:50:41 > 0:50:44and character of their children to chance.
0:50:46 > 0:50:49You've got two girls - are you certain you don't want a boy?
0:50:49 > 0:50:52- Yes, quite sure - we really do want another girl.- Yes, definitely.
0:50:52 > 0:50:56Right. Well, you've had a chance to view the data at home?
0:50:56 > 0:50:59Yes. We've narrowed it down to zygote 3 and 6 -
0:50:59 > 0:51:02we're not really sure which one to choose.
0:51:04 > 0:51:06What sort of characteristics were you thinking of?
0:51:06 > 0:51:08We definitely don't want to tamper
0:51:08 > 0:51:10- with the physical side of things in any way.- No, except that
0:51:10 > 0:51:13we would like her to have my father's red hair.
0:51:13 > 0:51:16Ah. Ah, well, that's easy.
0:51:16 > 0:51:19We can make her homozygous on the three hair colour genes.
0:51:21 > 0:51:24- What about her character and emotions?- Ah, well, yes,
0:51:24 > 0:51:27there are a few things we'd like to have modified if possible.
0:51:27 > 0:51:29We'd like to reduce shyness,
0:51:29 > 0:51:32and susceptibility to depression...
0:51:33 > 0:51:37..without necessarily damaging... any artistic potential.
0:51:37 > 0:51:41Also, we'd like her to be musical, and if possible,
0:51:41 > 0:51:43also we want her to be ambitious.
0:51:45 > 0:51:48A world where we could pre-order genetic traits for our children
0:51:48 > 0:51:51might seem fanciful, but in some ways,
0:51:51 > 0:51:54it's already here.
0:51:54 > 0:51:58IVF has given embryologists the opportunity to screen embryos
0:51:58 > 0:52:00for genetic problems.
0:52:00 > 0:52:03These techniques have helped women like Philippa Handyside,
0:52:03 > 0:52:06for whom having children was impossible.
0:52:09 > 0:52:12Just kept miscarrying all the time.
0:52:12 > 0:52:16And it just actually got quite normal - that was actually how awful it was.
0:52:16 > 0:52:19It was very hard, and it sounds really harsh,
0:52:19 > 0:52:22but you just kind of get... It just becomes part of life.
0:52:22 > 0:52:26I used to get pregnant, lose it, pregnant, lose it, and that was it.
0:52:35 > 0:52:39Philippa Handyside wasn't trying to create the perfect child -
0:52:39 > 0:52:41she just wanted to have a baby.
0:52:43 > 0:52:45But she wasn't having any luck.
0:52:46 > 0:52:51So she underwent testing to see why she was having so many miscarriages.
0:52:55 > 0:52:58The cause of her miscarriages was genetic -
0:52:58 > 0:53:00the result of a chromosome disorder.
0:53:01 > 0:53:04It meant most of her embryos didn't have the right combination of genes
0:53:04 > 0:53:07they needed to grow healthily.
0:53:08 > 0:53:12There was nothing Philippa's local hospital could do for her -
0:53:12 > 0:53:14it seemed she might never have children.
0:53:17 > 0:53:20But then, Philippa heard about a new technique.
0:53:21 > 0:53:25It's a technique some people think could lead to designer babies.
0:53:36 > 0:53:40The technique is called preimplantation genetic diagnosis,
0:53:40 > 0:53:42or PGD.
0:53:43 > 0:53:48Using PGD, scientists can screen embryos outside the womb,
0:53:48 > 0:53:50long before they develop into babies.
0:53:52 > 0:53:56Then, they can select just those embryos that carry healthy genes
0:53:56 > 0:53:59to ensure the baby is free from genetic abnormalities.
0:53:59 > 0:54:03PGD is one of those ideas that's so clever
0:54:03 > 0:54:06that it seems impossible to do. I mean, how could you possibly
0:54:06 > 0:54:09take a very early embryo and take out a cell and diagnose it?
0:54:09 > 0:54:12Well, in the end, it transpired that the embryo
0:54:12 > 0:54:14is such a tough little beast
0:54:14 > 0:54:16that it actually allows you to do fairly outrageous things to it,
0:54:16 > 0:54:18without noticing.
0:54:20 > 0:54:22To do PGD, the doctors first
0:54:22 > 0:54:26had to extract eggs from Philippa's ovaries.
0:54:27 > 0:54:32These eggs were then fertilised by her husband's sperm in a lab.
0:54:34 > 0:54:38The fertilised eggs were allowed to develop into a cluster of cells.
0:54:53 > 0:54:56You phone every day and you're told how they're getting on.
0:54:56 > 0:54:58It's like having children in nursery - you're told every day
0:54:58 > 0:55:01how they're progressing through.
0:55:02 > 0:55:05Then, 48 hours after fertilisation,
0:55:05 > 0:55:09acid was used to etch a hole in the membrane of each embryo,
0:55:09 > 0:55:12and a single cell sucked out.
0:55:19 > 0:55:21And on day three after their collection,
0:55:21 > 0:55:24we've taken a single cell from each embryo,
0:55:24 > 0:55:27and we've sent those cells to our genetics team across the road,
0:55:27 > 0:55:30so they can make the molecular diagnosis.
0:55:33 > 0:55:35The theory is that if the analysis
0:55:35 > 0:55:38shows the genes are normal in the single cell,
0:55:38 > 0:55:42then the embryo is came from will also be genetically normal.
0:55:42 > 0:55:45That's OK - two blue...
0:55:45 > 0:55:47Two green,
0:55:47 > 0:55:49two red, so that's fine.
0:55:51 > 0:55:54Eventually, they found cells from two of Philippa's embryos
0:55:54 > 0:55:56that had healthy genes.
0:55:57 > 0:55:59They called us through and said,
0:55:59 > 0:56:02"Yep, we've got a couple." The geneticist said,
0:56:02 > 0:56:05"There's one that... it's not divided so well,
0:56:05 > 0:56:08"but the other one, brilliant, absolutely brilliant.
0:56:08 > 0:56:13"So, we're going to implant, if you're happy, two back in."
0:56:13 > 0:56:17So, it was a case of, get ready, and get kind of...
0:56:17 > 0:56:22into the room, and ready to have the implantation...done.
0:56:25 > 0:56:27PGD allows mothers like Philippa
0:56:27 > 0:56:31to have children they would otherwise have been denied.
0:56:33 > 0:56:35But there are those who still worry
0:56:35 > 0:56:38that this is the thin end of the wedge,
0:56:38 > 0:56:41and that in the future, people would be able to select embryos
0:56:41 > 0:56:45on the basis of much more controversial genetic traits.
0:56:47 > 0:56:51The forefront of research into sex and fertility
0:56:51 > 0:56:54continues to present us with much trickier ethical problems
0:56:54 > 0:56:57then we've ever had to grapple with in the past.
0:56:59 > 0:57:02But at the same time, the science of sex
0:57:02 > 0:57:04has helped us learn about ourselves,
0:57:04 > 0:57:08to combat sexual problems and to restore fertility.
0:57:15 > 0:57:20Sex is still the most intimate and personal aspect of our lives.
0:57:20 > 0:57:23But since science got into bed with us,
0:57:23 > 0:57:27we've had a much better chance of decoding this tricky subject,
0:57:27 > 0:57:30and of understanding ourselves.
0:57:30 > 0:57:37We know so much more about sex now than we did just a few decades ago,
0:57:37 > 0:57:41and I think our lives are better for it.
0:57:51 > 0:57:54Subtitles by Red Bee Media Ltd