When your parents made you, they created a random mix of their genes. Around 20 thousand distinct genes make up your entire genome – a complete recipe, which describes all of you. Each gene is a puzzle piece of that genome – a self-contained snippet of code which describes a small part of you. The programming language this code is written in, is called DNA. Here’s the catch – every gene, which you received from either one of your parents is, in fact, only a copy of their original gene. And not all copies are perfect. Mistakes are made! And so it happens, that some of your genes are similar, but slightly different from the parent genes they were copied from.
Each gene consists of an average 150 thousand base pairs, the basic DNA building blocks. Copying each of them in the right order for each of your 20 thousand genes is hard, so nature screws up here and there. Those mistakes are not aimed towards any goal – they’re just mistakes! In biology, those mistakes are called random mutation. If you make a random change to something that works really well, you are likely to end up with something that works less well. In fact, most random mutations produce bad results: Slightly worse eye sight. Slightly less fertility. Slightly worse immune system. And so on. Then how on earth did random mutation help us evolve our way up the hierarchy towards world domination? The answer is: selection.
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While most mutations produce very slight disadvantages, some mutations are benign and some randomly produce slight advantages. All you need to do is chose the best, and discard the rest. Nature is doing just that: In our evolutionary history, there have been 2 great selectors: mating and death. If you die before you can mate, your specific gene mutations are removed from the gene pool. If you manage to stay alive, but can’t attract a mating partner, they are also removed from the gene pool. Only if you manage to survive long enough and attract a mating partner, your genes – or, more precisely, a copy of some of them – make it into the next round. These are the boxes your body has to tick. And since each gene describes a small part of you, each gene contributes a small part towards ticking those boxes. The effect a gene’s code has on you is called its phenotype. These effects can be physical, like making you a bit more athletic, or neural like making you a bit more empathetic. Those would be good gene mutation, which produce phenotypes, which make it slightly more likely your body meets those goals. Whereas a bad gene mutation produces a phenotype, that makes it slightly less likely your body meets those goals. The accumulation of the phenotypes of all your genes and their specific mutations determines how likely you are to pass them on. Of course, even in wild nature, it’s not only ever the very best genes, which make the race. You could be not the best looking, not the most sporty and not the most healthy, but still manage to pass your genes on to the next generation. On the other hand, you could be perfectly healthy, cautious, above average intelligence and still have bad luck. But over the course of millions of years and and hundreds of thousands of generations, this combination of creating a range of mutations and then selecting for the best, will result in the better genes, which produce slight advantages each step of the way, consistently ending up in the next generation. While the worse genes, which produce slight disadvantages, will fail more often than not to be passed on. Consistent slight advantages compounded over a loooong timeline can produce huge advantages in the end. It’s like consistently investing $1 into the stock market each month. It might seem like a completely insignificant saving month over month. But if your family had done so since 1918, then in 2018 those savings would be worth around $1.8 million dollars. Instead of 100 years in the stock market, our gene pool has had millions of years of mutation and selection. Through those 2 mechanisms, Darwinian evolution has consistently compounded advantages and got us where we are today. And then everything changed. You are the result of an unbroken chain of hundreds of thousands of ancestors, all of whom managed to not die young and attract a mate. And your job is to not break this chain. But let’s be real: you are playing the game on easy settings. What we call civilisation is, in evolutionary terms, a giant selection pressure remover. You don’t have to run from tigers, hunt your own food, or survive in a hostile environment. You live in a world in which we have isolated ourselves from wild nature and are surrounding us with things to keep death as far away as possible. Because Also gone is the alpha-male societal structure, which has shaped much of our evolutionary history – replaced by a monogamous world, where everybody gets to chose 1 mating partner – mostly… There is a whole match-making industry built around everyone’s urge to get their genes into the next generation. Given, that these two are the fundamental drivers our genes have been selected for, for millions of years, it’s really no surprise, that in the modern economy, those are the two fields we’re pouring a major part of our money and attention into. But our ambitions to solve death and match-making have resulted in a paradox: If we remove the very selection pressures that made us – the pressure to select for the good genes – aren’t we worsening our condition in the long run? Won’t the overall quality of humanity’s gene pool decline? The answer is: Yes. Sort of. But actually, not really, as you will see at the end. But first things first: if we remove selection pressures, we – unintentionally – help the bad gene mutations stay around. And because bad gene mutations are more frequent, they will outnumber the good ones in each successive generation. Compounding these disadvantages over time will make us end up with a clear gene pool decline. That’s a nice theory, you say, but can we actually observe a gene pool decline in our societies today? Now this is where we dive into speculation territory! Evolution – in complex life forms like humans – operates on very long timescales, so it’s not easy to determine which of the changes we might be seeing in ourselves are actually lasting evolutionary changes. As far as we can tell, we are – genetically – pretty much identical to our ancestors from around 30 thousand years ago – the so called anatomically modern humans. But this view point might change, as we continue to gather historic human DNA samples, and even more importantly better our mapping of which multifactorial effects each gene has. With all those blanks, making any predictions about a possible future gene pool development is tricky. That being said – it’s great stupid fun – here we go. Number 1: Bad eyesight. There are many theories as to why an ever larger group of the population is in dire need of subscription glasses, contact lenses and/ or laser eye surgery. One contributing factor might be that humans haven’t really been selected for eyesight in maaany generations. The selection pressure for good eye sight started being removed when the first humans settled down in villages, around 10 thousand years ago. Even on an evolutionary time-scale, that’s something. And without any selection pressures, not only is there no improvement, but there is stagnation, because most mutations are bad – remember? Ok, but how can something that has evolved to natural perfection in millions of years measurably deteriorate in only a few thousand years? The answer is: mutation rate. Without selection pressures, the mutation rate is at its maximum speed, whereas applying selection pressures reduces a population’s mutation rate. That’s because evolving something to perfection – for a specific purpose – is an uphill battle. You’re relying on a small lucky number of positive mutations, which nature can select for. Without selection pressures, the majority of bad mutations is passed on. It’s not only going downhill, but also at a way faster rate. So called regressive evolution is well studied for eyesight in some cave animals. The Mexican tetra, for example – a common aquarium fish – has a not so distant cousin, called the blind cave tetra. This branch of the species ended up living in underwater caves some generations ago, where it completely lost the eye sight its ancestors had. This is not, because having no eye sight in caves is some sort of advantage. It simply lost it, because bad mutations added up over time and there were no selection pressures pushing against degenerative eyes. As for humans, we don’t know how good or bad the eye sight of those first settlers really was. For most of history things haven’t exactly been recorded very reliably. So it’s hard to say how much regressive evolution has actually occurred for our eyes so far. But if the blind cave tetra is our canary in the coal mine, then we are – slowly – headed for disaster. Number 2: Infertility. The inability or struggle to have children of your own is fairly frequent in humans – who would have guessed…. There are many potential reasons why a couple wouldn’t be able to have kids naturally. But if you can’t pass on your genes, you’re out of the gene pool, right? Not anymore. We have developed technology to bypass natural infertility in many cases. The most prominent example being so called IVF, or in vitro fertilisation. IVF has existed for 35 years now – or more than one generation. So far it has helped millions of couples, who were struggling to get pregnant, to fulfil their wish to become parents. And that’s wonderful. Now if the parents’ fertility struggles originated in an unfortunate combination of gene expressions, then their kids will likely carry them on. A study by the University of Brussels analysed 54 young adults, who were conceived through IVF. On average, they showed less than half the fertility of naturally conceived adults their age. If that trend holds, it’s likely another example of regressive evolution. Those are just 2 ways in which our collective gene pool might be declining. And by analogy, this list could be extended to things like general health and general athleticism. Are we turning ourselves into mere blobs of existence? Was wall-e right? Before you request anarchy and the destruction of our civilisation, consider this: Never in history have more people actually been healthier, were able to get better vision, or were more able to have healthy kids of their own. We seem to be doing all right. That’s because any possible regressive evolution has been far outpaced by the advances of technological progress. We are the most capable package of biology plus technology, that has ever existed. And technology is becoming more than just a patch for our biological short comings. It’s starting to actively feed back and curate our biology. PIGD, or pre-implantation genetic diagnosis, allows us to screen embryos for genetic diseases and artificially select those genomes that produce healthier kids. Even more fancy than that is CRISPR, the brand new gene editing tool we have taken from bacteria. It may allow us to not only counter regressive evolution, but potentially positively edit our collective gene pool, should we chose to do so. There is much public discourse in this field already, and even more to be had. With such possibilities, instead of a gene pool decline, we might very well be on the brink of the opposite. We might see ourselves turn into perfect, immortal super-humans. But whether we become homo deus or homo degenerate, it will all happen long long after this video has ended. I’d like to give a quick shout out to Mikme – a young and innovative microphone maker from Austria. They’ve gifted me one of their microphones to try out and – in fact – this very video has been recorded on it. I couldn’t be happier with the result, check them out. Link’s in the description.