h [Music] [Applause] [Music] I'm going to be 8-year-old neighbors Darren Bruff and Natalie Jackson don't realize that their childhood days are numbered that their purpose on this planet is to reproduce and pass on their [Music] genes but their immature bodies aren't yet up to the [Music] task deep in Natalie's abdomen are her ovaries inside her blood feeds half a million spherical cocoons called follicles hidden within each follicle is an immature egg but for now they're in suspended [Music] animation in Darren's testicles nothing much is happening either though there are millions of cells there are no signs of sperm the cells destined to create them lie dormant Natalie's and Darren's sex organs are waiting for a signal that will bring them to life Natalie a signal that will trigger puberty puberty begins years before there are any outward signs no one knows why but it always starts at night driven by the body's command CER the brain deep in Darren's brain a group of cells is activated [Music] for the first time ever the cells release a chemical signal into the tiny blood vessels around them hormones known as genotropin fly through his blood these chemical Messengers carry signals from Darren's brain to the rest of his body night after night the hormones flood into his bloodstream and begin to take [Music] effect inside his testicles cells begin to divide they organized themselves into tubes building factories which will one day produce [Music] sperm as the years pass Darren's brain step up the pace the signal gets stronger and the changes taking place in Darren's testicles get faster and faster between the newly grown tubes gonat trovin seep out and soak into specialized cells triggering them to produce the male sex hormone it's name [Music] testosterone mom by the time Darren is 13 come on now he has amassed enough testosterone to begin to change his boy's body into the body of a man Natalie Natalie get up it's [Music] 8:15 come on Natalie you'll miss the [Music] audition the changes in Darren mean he'll soon be able to reproduce but to be a mature adult he also has to want to inside his brain testosterone seeps from blood vessels into the fluid which surrounds his brain cells soon it will transform his mind next n Natasha Watson sir what I doing here J know we just have to B they finished Natasha you know David glae he's reading Romeo right off you go David yo yo yo is what I've got to get it's Mickey D with my Juliet oh Romeo oh but we hit a snag why does monu have to be your tag next inside Darren's brain testosterone now soaks through the membranes of dormant cells triggering a chemical reaction the testosterone brings to life a group of interconnected brain cells this is Darren's reproductive circuit it gives him the desire for sex let's try some singing name Natalie Jackson sir the world willake I [Music] Darren has something new to cope with a sex drive and the girl next door has become the woman of his dreams that much good that much good and this much bad it's the only name I ever had but for you my love I would change it now just click on my heart and find out how [Music] and this one you've got to try this one it's got a tiny smell and I'm sure that would smell lovely this one lovely as well have a smell of that it's wonderful quite refreshing and what about this one now this one's much nicer it's much over the past 5 years Natalie's brain has been just as active as Darren's I've got to try this one but while ganat trofin transform form his testicles they bring to life her ovaries the hormone has stimulated a few of the follicles to grow so that the eggs concealed inside them begin to mature as the follicle wall grows and swells a new hormone seeps out the female sex hormone estrogen it flows out of the follicles into her blood sh it's estrogen will drive Natalie's transformation into a sexually mature woman show this wonderful green shade now don't worry about it it looks very nice and as you can see it's very subtle now also we can show you a ni all that would really M that's gorgeous like David BL yeah you might be gorgeous but you can't sing so so it's meant to be a musical you get to Snug the best looking broke in school yeah oh yeah but nothing forget about his singing once you start kissing are you wearing perfume inside Natalie's brain estrogen is making permanent changes inactive areas of her brain are coming to life this is probably because the hormones stimulate nerve endings encouraging them to form new connections these new circuits fire powerful new emot I'm getting a tattoo you are you are not I might have known known what you automatically say no no no no no no Natalie's feelings are suddenly much stronger but she hasn't yet learned how to control them no you never let me do what I want you are so predictable no we're not calm down dear I don't even know why you had me in the first place and while Natalie must learn to live with estrich Darren is in the grip of testosterone Darren what are you doing Darren is trying to cope with a brain that wants sex a bit a bit of gardening why what are you doing having supper outside my dad went mental I told him I was getting a tattoo you're getting a tattoo where well either here or here what do you think his reproductive circuit is interfering with his ability to hold a conversation leaving him tongue tired I'm paying you to get in the school play I was there for the auditions doing what waiting for band practice oh right I going to be in the play as well I didn't know you into drama Mr passel he wanted an engineer a what someone who hasn't done it before like a virgin yeah I suppose the see rehearsals then yeah like all men Darren's hormone levels soore at night as testosterone Rises his reproductive circuit goes into overdrive and even takes control of his [Music] dreams next so we decied where you want it I don't know what do you [Music] think now his reproductive circuit is so overstimulated it sends a signal down on his spine to his penis his penis is constructed of interconnected Caverns blood rushes in filling the caverns and making them expand Darren's penis has swollen to five times its normal size [Music] [Applause] [Music] oh mom come on up come on love it's after eight Bye Mom oh hi hi Natalie started puberty later than Darren but she is growing much faster than him and looks more mature all thanks to [Music] estrogen put to run when estrogen and her body reached a critical level it triggered a growth spurt since then special plates in Her Bones have been growing [Music] rapidly to catch up with Natalie Darren needs his own supply of estrogen his brain has a remarkable way to manufacture the hormone it converts excess testosterone into [Music] estrogen sadly for Darren it takes time for estrogen to build up which is why boys seem to mature more slowly than girls and why girls are usually more interested in older boys but just as Darren needs estrogen Natalie needs the male sex hormone testosterone her adrenal glands which sit on top of her kidneys pump small amounts of testosterone into her blood her blood carries it to her brain where it seeps into the surrounding cells stimulating her reproductive circuit and giving her the sex drive she needs to further the interests of her jeans all right oh hi looking good T so what's up how' you VY going out with me going out where wherever you want so all right nice one there's more to testosterone than creating a sex drive it also gives Darren drives to help him get sex he is more competitive and assertive than ever before come for band practice I won't be two tick why come for band practice sir I want to part in the play I didn't know you acted I'm an engineer are you now and I can see Darren doesn't know it but changes inside his testicles are bringing him closer to furthering his genes deep within the wall of a tube a dormant cell is coming to life the cell divides the new cell that is formed will become Darren's very first sperm Romeo and Juliet in rap monteu verses capulets with music Monte's Sopranos all capulets alos and tenners I want all the monus to have unbroken voices Romeo's a monu I'm a tenner exactly how would you feel about playing tibolt I'm Romeo the fiery so wicked so manly so much more like you David so who's going to be Romeo meet your new Arch Enemy Darren Bruff and Natalie let me introduce you to your new love interest Natalie thinks she is more mature than Darren but her body is no closer than his to being able to reproduce in her ovary her enlarged follicles continue to grow but they need to swell to 100 times this size before the eggs contained within them can reach maturity [Music] [Laughter] [Music] Darren and Natalie are losing control of their bodies to hormones the levels of testosterone and estrogen in their blood are rising with every passing day slowly transforming their bodies to prepare them for sex [Music] [Music] [Applause] one of the main objectives of sex hormones is to trigger changes which will make them more attractive to potential mates but sometimes the effect is just the opposite last night Darren had a testosterone surge with unfortunate consequences [Music] deep in his pores are tiny glands called sebaceous glands sebum should flow out of the gland and up onto the skin but Darren is producing so much that it clogs his pores it becomes a breeding ground for bacteria the poor is infected sebum gave our ape ancestors glossy coats making them attractive to other Apes all that gives Darren is [Music] pimples yeah you know she's all right Natalie is luckier she too produces sebum but estrogen keeps the levels down reducing the effects on her skin for now what's wrong with his face he's wearing makeup or pizza face Natalie thinks you're wearing [Laughter] [Applause] makeup Darren's body is overreacting to escalating hormone levels and pimples are not the only result oh come on man testosterone has made his genitals so sensitive that even the slightest touch can trigger a response the caverns of his penis are filling up again but this reaction is a reflex his brain is not [Music] involved Darren's penis seems to have a mind of its own I make way to that deep in fact it's quite common for teenage boys to suffer as many as 20 reflex erections a day while Darren suffers at the hand of hormones Natalie is benefiting until recently there were a few visible differences between her body and a boy but sex hormones are now in her body into a different shape designed to be attractive to [Music] men under the influence of estrogen in Natalie's chest fat globules are sucked out of her blood by surrounding fat cells the cells soak up the fat and as they expand so do Natalie's breasts the same things are happening to the fat cells on her hips and buttocks giving Natalie the first signs of womanly curves o what I'm a mate we look out for each other look I've had enough of this I'm going to look at some trainers shallow I know shallow in [Music] testosterone's been nothing but trouble for Darren but he now has enough for his brain to convert into estrogen finally triggering his growth [Music] spurt his skeleton is lengthening at a rate of half an inch a month faster than any time since he was a baby being taller will help make Darren and more attractive to girls but in the short term such rapid growth has its drawbacks yo yo yo we in a place to be on the wheels of still MC easy now hey man can't believe my eyes that girl's got to be my prize don't go there that's not for you she culate mind take you as Darren moves around his brain must track exactly where every part of his body is to keep his movement [Music] coordinated but now that his limbs have grown his brain must adjust no way Uncle this is our place I makeing sorry that he show his face leave Young Blood I mean it to don't even want to up there and because his legs have grown so quickly his brain just can't keep up Darren's hormones are working to make him more and more sexually attractive his muscles are made up of fibrous strands testosterone makes these fibers multiply causing the muscle to thicken bulking up his biceps but the fastest multiplying cells in Darren's body are in his penis [Music] [Music] Natalie's Sex Drive is kept active by testosterone but the hormone also has a surprise in store [Music] inside pores in her groin and armpits testosterone seeps out of her blood and stimulates hairs to grow over time they extend up the poe to the surface of her skin [Music] [Applause] in the space of 1 month Natalie has grown 60 ft of pubic and armpit hair we have our chemistry now for our explosion the first kiss Shall We Begin from gone and live gone and live stay and die love you girl and you wonder why it may not feel like it but Natalie's new hair is another attempt by her body to attract a mate is the hairs are designed to trap sweat in fact a hairy armpit can hold 30 times more sweat than a hairless one bacteria living on her skin Feast on the sweat they excrete waste in the form of gas with a powerful OD a text from a home girl saying Chow three words mother bedroom now come out the window before she comes you should have gone when we saw the sun Bo is an outward sign of Natalie's emerging sexual maturity our ancestors found it attractive come over here and don't to dis me ain't going nowhere until you but in our hygiene conscious World Bo tends to have the oppos effect ain't going no until you kiss me more passion Darren more passion all the changes in Natalie's body are designed to Aid a process still unfolding in her ovaries inside the gonat tropins have caused one follicle to grow so large that the egg concealed inside it is almost mature this one follicle is now producing 3/4 of all the estrogen in her body but the is a problem the bigger it grows the more ganat tropin it needs to survive and Natalie's brain can't yet manufacture enough starved of hormones the follicle starts to die killing the egg inside [Music] it it stops producing estrogen causing the levels in Natalie's body to plummet soon the results will start to show within 2 days there is no longer enough estrogen in Natalie's skin to keep sebum production down it's Natalie's turn to get [Music] pimples the shortage of estrogen is having even more drastic effects beneath her skin inside her womb layers of cells form a lining designed to sustain a growing fetus but without estrogen blood vessels that feed these cells are cut off in a few hours time Natalie's womb lining will die Natalie shimone over here don't think so squeaky boy don't think so what I don't think that she's interested although I know you do um speak highly of her Natalie's estrogen levels have collapsed but Darren's testosterone levels keep going up result increased [Music] aggression for our distant ancestors fighting for a mate was a necessary skill for the sexually mature male in fact fact men's Brains are wired so that circuits for aggression and sex [Music] overlap inside Natalie's womb the cells which make up its lining have died now layer by layer they begin to Shear off Natalie is having her first period mom mom next door Darren is about to experience a less visible but equally dramatic change sperm production lines have begun throughout his testicles as new cells are made they're pushed up against the walls of the tubes one cell is forced right through the wall now a remarkable transformation Begins the cell's DNA containing Darren's genes is squeezed into a tiny head the rest of the cell forms a long thin tail this is Darren's first sperm unable to swim yet the sperm is carried away by contractions of the [Music] tube L me for you hi Simone yeah my mom she's mental Natalie is suffering all the discomforts of a period but this first period is unique because it hasn't been triggered by the creation of a fertile egg your mom let me in so what's wrong with you oh it's a woman thing so you're not coming out sorry about that maybe I'll have to take someone else to the precinct to watch you get beaten up maybe I will maybe I'll take Simone I don't think so this woman think made you dead boring oh get lost Natalie's first period is a major Milestone of puberty but she's still incapable of [Music] reproduction while Darren is now making spur oh hi Natalie has yet to make a mature egg at the age of 13 Natalie's body is locked into a monthly cycle by her [Music] brain her brain cells Drive the release of genotropin once again in her ovary the hormone stimulates follicles to grow with one larger than any [Music] other the follicles saturate her body with estrogen it travels to her womb cells and triggers them to [Music] multiply in the space of 10 days her womb line has completely regrown sorry about you and David oh he's an idiot so about Dar and KN no it's not going to happen for us know what I mean you know where this is heading don't [Music] you in Darren's testicles the production line is picking up pace but it will still be another 5 years before a sperm factories work at full capacity churning out 1,000 sperm every second now his sperm collect in a chamber ready and waiting to fertilize an egg well girlfri how fine is [Music] [Applause] [Music] [Applause] you yo yo yo we in the place to be on the wheels oful MC go go hey man can't believe my eyes Z go got to be my prize don't go there that's not for you she you while Darren's testicles make millions of sperm Natalie's ovaries concentrate on producing just one perfect egg this time the enlarged follicle is doing everything in its power to stay alive until the egg concealed inside reaches maturity black vessels grow all over it to bring extra nourishment as it reaches a critical size the follicle sends a signal to Natalie's brain triggering a massive surge of hormones the biggest pulse of genotropin her body has ever experienced the hormone reaches the egg inside the follicle finally stimulating it to mature no way uncle this is our place I'll make him sorry that he showed his face leave it Young Blood I mean it dread don't need no one to wind up dead testosterone has one last cruel trick to play on [Applause] [Music] Darren stay the levels in his blood are now high enough to trigger the cells in his vocal cords to [Music] multiply his vocal cords are having their own growth spur believe it is the morning you told me that you stay all night promised everything would be all right and now you're going to run away as Darren's vocal cords get longer his voice will get deeper [Music] I could stay you know I would I've come it feels so good but just as in his arms and legs it's difficult for Darren's brain to properly control his vocal cords now that they are a different length from those his brain is used [Music] to life a text from a home girl saying chow and three words mother bedroom now climb out the window before she comes you should have gone when we saw the sun now Darren can't trust himself to speak at all farewell to you my lover and my friend better do want a kiss before you [Applause] [Music] descend Tumi please please [Music] [Applause] [Music] Natalie is about to experience the most momentous event of [Music] puberty her body is ready to release her first mature egg the wall of her ovary is stretched to the breaking point the egg bursts out of its follicle and right through the ovary wall one one of her Fallopian tubes carries it toward her womb in 2 weeks time this egg will be swept away in another period but it's the first of nearly 500 eggs that Natalie will produce one every month for around the next 40 [Music] years Darren is about to find out that he's reached sexual maturity signals from his reproductive circuit tell the chamber which holds his sperm to [Music] contract for the first time Darren's genes are set free into the world [Music] Darren and Natalie are now capable of reproduction but it will still be several years before they reach adulthood by Mom humans are the only animals to experience such a long drawn out puberty probably because we need time to learn the complex rules of our species before sex gets in the way [Music]