We’ve always been interested in sexual health. Way back in Ancient Rome and Greece, the most esteemed thinkers always had sex on the brain and we’ve never really shaken that habit. Still, back then these thinkers didn’t really know the inner workings of the birds and the bees, nor did they understand the role sex plays in your wellbeing. In the 1st Century AD, for example, Roman writer Pliny warned that intercourse would taint lactating women’s breast milk. Luckily, we’ve come a long way since then, thanks to five very important discoveries about sex.
1. Sperm under the microscope: In 1677, you might think Anton von Leeuwenhoek was pretty weird for taking a gander at his own semen sample in a homemade microscope – especially as von Leeuwenhoek got into microscopes on a lark as a hobby from his day job as a draper, or cloth salesman. However, this observation revealed human spermatozoa for the first time in history, with Leeuwenhoek spying ‘a multitude of live animalcules more than a million, having the size of a grain of sand,’ as he wrote to London’s Royal Society in November 1677. That said, Cristen Conger, wellness writer and co-host of the popular Stuff Mom Never Told You podcast, notes that although this was a breakthrough moment in sexual health history, ‘it would still take a while to get the record straight about how sperm contribute to the baby-making process. Von Leeuwenhoek’s contemporaries, in fact, imagined each sperm contained a tiny person, wishing and hoping to be delivered safely to a female womb.’
2. The egg’s time to shine: As female eggs aren’t as observable as male semen, it wasn’t until 150 years after Anton Von Leeuwenhoek saw sperm that Prussian-Estonian embryologist Dr. Karl Ernst von Baer viewed the human ovum. ‘von Baer’s observations of dog embryos led him to correctly outline the development of the human egg and explain the ovum’s cross-mammalian reproductive role in his landmark 1827 paper entitled “On the Genesis of the Ovum of Mammals and of Man”,’ Conger explains. ‘Ironically, this egg pioneer still dismissed sperm as useless in fertilization, exemplifying the simmering uncertainty over how exactly the ovum and those eel-tailed swimmers interact.’
3. Two become one: Conger details, ‘When reproductive fertilisation piqued the interest of German scientist Wilhelm August Oscar Hertwig in the early 1870s, the field was dominated by two conflicting – and ultimately incorrect – theories. One camp posited that the mechanical vibrations of so many wiggling sperm around an egg triggered embryonic development, like a clap light switching on in response to the auditory transmission. The other predominating view maintained that sperm deposit a chemical compound into the egg, providing the crucial ingredient to kick-start the process.’ However, Hertwig disproved his academic cohorts when, in 1872, he closely observed fertilisation in a transparent species of sea urchin and witnessed the fusion of sperm and egg. Moreover, he discovered that the process isn’t a group effort by all the sperm involved in a single ejaculate; it only requires a single sperm to find its way inside the egg.
4. The menstrual cycle map: ‘Before the late 1920s, doctors had modelled women’s fertility on the mammalian oestrous cycle, in which females go into heat, since the role of hormones was unknown at the time,’ says Conger. ‘In some species, if the cyclical window of fertility doesn’t result in pregnancy, endometrial lining will shed, similar to having a period. By that logic, scientists presumed that menstruation and ovulation were likewise co-dependent, or that ovulation merely happened spontaneously.’ However, in 1927 and 1928, the research team of Edgar Allen and Edward A. Doisy isolated and identified the roles of the hormones progesterone and oestrogen, respectively, enabling the scientists to map out the menstrual cycle as well as ovulation.
