Death and Sex 

Don’t misunderstand me: I’m not talking about death from a case of over-exertion. I’m writing about biology. If we’re honest, most of us humans are pretty pissed that one day we’ll have to die. It’s been somewhat of a preoccupation of humans for thousands of years. Most anthropologists would explain the early origin of religions as a way by which humans have tried to deal with this, with promises of a next stage.

Just in case anyone is in the way of thinking that death is a curse put upon us following some sin in the Garden of Eden, let me explain that sex was a great advance in evolution that makes it possible for us to exist at all. If you were really hoping to live eternally you should have been born a germ. All the bacteria and other single-celled organisms, such as amoebas, alive today represent a continuity of living protoplasm over the last three plus billion years. They have just kept growing and dividing in half when they got a bit big. Of course not every individual is still alive otherwise we’d be drowning in bugs. But there has to have been a continuity of their protoplasm. More on that later.

A long time ago, some of these single cells stayed stuck together and the ‘idea’ of multicellular organisms began. Now the planet is populated by millions of species of multicellular plants and animals all with finite lifespans. Some insects live just a matter of days, some trees live a few thousand years, but we all, because of our multicellular nature, have to die. Our human bodies are made up of approximately 300 billion cells. You can’t just make a duplicate copy of that bag of complexity. All we complex creatures can do is produce some microscopic special cells that will grow into a whole new billion-cell life form. We die and they take our place. 

OK, so then why don’t we all just produce some genetic copies of ourselves in single-cell form, sort of ‘virgin birth’? Why sex? We’re told that evolution works through survival of the fittest, or more precisely survival of the one that has most kids. But if I could just bud off a copy of myself, in a year or two I’d have two offspring; whereas with sexual reproduction it takes two people to produce one offspring; so the math doesn’t add up. Here’s the point. Most of us have heard of mutations – little changes in the DNA that occur from time to time and are often not a good thing (can lead to cancer), but just sometimes by sheer luck produce an improvement. Since the beginning of time that little bit of luck has been what evolution has worked on to develop/evolve slightly improved models. But if it was that alone we’d still be looking like slugs. 

What sex loses in numbers of offspring per individual it makes up for in recombination. This is the reshuffling of our DNA as our gametes are produced.  It’s called meiosis. This is why no matter how many children a couple has, unless they’re identical twins they’ll all be fascinatingly different. Over the last billion years or so evolution has played on this great variety produced by sexual reproduction and the result is not only the wonderful variety of plants and animals in our world, but also ourselves. If sex hadn’t been ‘invented’ we wouldn’t be here. But, to return to my opener, the pay-off is that our individual bodies do wear out and die. 

But remember those ancient bacteria that began it all? They’re closer than you think. When early multicellular organisms started to develop, one challenge was to deliver energy locally in the larger more complex cells. Either by kidnapping or a friendly deal – “I’ll protect you if you’ll work for me.” – some small aerobic bacteria got swallowed up into the cells of the multicellular organism. They’re still there today in every cell of our bodies – called mitochondria, the ‘powercells’ where glucose is ‘burnt’ to produce energy, still with their own separate thread of DNA handed down from all those billion years ago. 

A man’s sperm is simply a tiny packet of half his genetic material. You got your mitochondria from your mother and so on back down the female line. Incredibly, only about 33 different lines of mitochondria have been found amongst all human beings! I’ve had mine tested and so I know that my mother’s mother’s mother’s people had been in northwest Europe for approximately 30,000 years. 

A human egg cell is quite large as cells go, containing many thousand mitochondria embedded in protoplasm representing a continuity of living tissue since the beginning of life on this planet. So ladies, you are part of an ‘eternal life’, and, because of sex, we guys can at least hand on a few molecules of DNA. 

Enjoy !