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We’re not evolving

Evolution has never been more popular than it is now, and rightly so. Darwin’s legacy is one of the most potent ideas ever. Not only is it a crushingly powerful explanation of life, but its core mechanisms of reproduction, variation, and selection apply to all sorts of other domains. Technology, memes, and capitalism are common examples, but they’re just the beginning.

We can take it a bit overboard, though, especially when we start navel gazing and wonder how humans are evolving. We don’t yet have square, keyboard-friendly fingers, or ears with perfect earbud-shaped holes, but are we evolving shorter attention spans, more Asperger’s syndrome, or faster video game twitch reflexes?

No, we’re not. First, evolution takes a long time: thousands, even millions of generations to see real changes in a phenotype. All of recorded history is still just a couple hundred generations old. Technology and other changes in modern life affect us profoundly on the nurture side, but not so much (yet) on the nature side.

We’ve also intercepted two of evolution’s three legs, selection and reproduction, and thrown them wildly off course. Modern medicine may not be perfect, but it does ensure that most babies survive into their adult, childbearing years, regardless of their innate health or fitness. That throws selection out the window.

As for reproduction, you probably know at least a few happy couples who have chosen not to have children. Widespread birth control had a profound, unprecedented effect on our species when it unshackled sex from procreation. It also had an important side effect: unlike animals, the fittest people no longer had the most or strongest children.

(Another surprising side effect is that we’re all having too few children. The developed world has plummeted far below the replacement rate, and it’s only getting worse. Labor markets have shrunk across the world, especially in developed regions like the EU and Japan where economies are already stagnating. So much for Malthus and Ehrlich.)

We may have disintermediated selection and reproduction, but variation is still intact. IVF, surrogates, and adoption haven’t changed the fact that sperm and egg still mix DNA randomly to make a baby, and they still do it with good old RNA transcription, an amazingly good natural process that nevertheless lets the occasional mutation slip through.

Sure, epigenetics is all the rage these days, and it incorporates the environment, and it’s even hereditary, but it still just turns our existing genes on and off. Epigenetics still doesn’t provide any evidence for Lamarckian style inheritance of skills you acquire during your lifetime, and no one expects it ever will.

It’s definitely fun (slash worrying) to think about how we’re adapting to technology and modern life. Responses range from techno-utopianism to “kids these days, get off my lawn!” The human brain is amazingly plastic, especially when we’re young, so yes, iPads and Facebook and video chat leave their mark on us. That’s not evolution though, and it’s silly to pretend it is, if not downright intellectually dishonest. Evolution isn’t that good, or that fast, and it doesn’t matter since we’ve pulled the plug on it anyway.

The real conclusion isn’t that we’re evolving, but that all sorts of other things are, in entirely new environments. Startups compete, multiply, and often exit or fold in just a few years. Their products have even shorter lifespans. Superbugs evolve resistence to antibiotics by cranking out hundreds or even thousands of generations in under a year. Internet memes spread like wildfire overnight. Culture, politics, art, and many other parts of the modern world evolve at a speed we can appreciate, leaving artifacts we can see and touch.

If you want to see evolution in action, that’s where it’s at. Forget the pseudoscience; humans aren’t evolving right now, and that’s ok. There’s so much of it going on everywhere else!

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17 thoughts on “We’re not evolving

  1. thanks! added to my list. Dennett is great, I love the stuff of his I have read.

    so I take it you do believe humans have evolved biologically in the last few hundred or thousand years? I’d love to hear the cliff notes explanation of why.

  2. One of my all-time favorite books is Dawkins’ book http://www.amazon.com/The-Selfish-Gene-Edition-Introduction/dp/0199291152  because it sheds so much light on life processes. Dawkins’ later books, however, are easier to follow than this one.

    http://en.wikipedia.org/wiki/The_Selfish_Gene

    It helps going in to know the most basic thing about game theory mathematics. In a game, you and your opponent pick a strategy, then game theory computes the probabilities of the different outcomes. With DNA, the alternative genes that compete for the same spot on the genome act like “strategies” and lead to outcome probabilities in the same way. The historical term can be misleading since there’s no conscious choice involved.

  3. Three things I can think of that are missing from your narrative.  The first is the impact of diet – consider lactose intolerance, which is largely absent from people of northern european descent.  This is largely due to a recent (relatively) diet high in dairy products in that region.  The second is parasites and diseases – sickle cell anemia being the classic example (or consider the bubonic plague – it wiped out some huge % of the population in the 14th century and its still around, but not so much of a, er, plague because we're all descended from the survivors).  The third one is climate – Inuit are well known to be much more cold resistant than other people (i don't recall what the specifics of the mechanism are).  Most of these changes are relatively recent (last 10K years) changes.

    The naive view of evolution is based on the notion that somehow we should be getting 'better' in some absolute sense, but evolution is a random process, so that concept is meaningless – better compared to what? via Google+

  4. got it, thanks. fortunately, i don't know that we're actually disagreeing. i was responding to the idea that we've evolved over the last decades or centuries, based on media, modern technology, etc. you're looking at 10k years, which i agree is enough time to start to see true evolutionary adaptation, especially since most of it came before we started seriously mucking with human reproduction and selection.

    plague in particular is an interesting case of "extreme" selection due to an event, as opposed to steady(ish) state environment. i hadn't considered that idea before.

    and you're right, people do often wrongly ascribe some kind of intent or goodness to evolution. variation definitely is random, but i wouldn't quite call evolution as a whole random, since selection and fitness do provide a direction. i expect that part leads most people's intuition to the framing of "better". via Google+

  5. cool! i missed that paragraph. for sake of discussion – the hand we’re dealt isn’t changing, but if the rules of the game are changed to affect the cards we play more or less permanently, isn’t the end result kind of similar? tangentially (and now i’m just being argumentative ;) while natural selection may not be in play across our species anymore, isn’t artificial selection still a possibility? technology has given us unprecedented capacity for travel, people have greater access to tools that allow sub-selection (e.g. internet dating that focuses on specific groups / personalities), and even culturally we seem to be congregating similar people into certain areas (silicon valley…), so i’d think that the potential for artificial selection in our species is at a high point via Facebook

  6. yeah, i should have framed my original post better and summarized what i was reacting to. for example, people often say things like “we’re evolving to multitask better.” not quite. we can fake it (poorly), but we can’t actually multitask, we have no multitasking card to play, so epigenetics can’t really help much.

    re artificial selection, true. people have definitely always married and had kids with other similar people, and may be doing that more, and that may intensify certain attributes. Asperger’s is the well-worn example. i’d come back to the time scale problem though. it’s not evolution until we can say that e.g. Silicon Valley engineers have biologically differentiated into a truly new species, and that’s at least a few hundred thousand years away.

    (and np, argumentative is fun! call it debate. :P) via Facebook

  7. "Better" = better adapted to the environment for reproductive success. The environment includes food, threats, and the other genes in the gene pool. Reproductive success includes kin selection (helping reproductive success of kin).

    For most of the world, there's no longer selection pressure for 20-20 eyesight. via Google+

  8. It seems to me that there are two questions that are being conflated: 1) Can evolution happen on short time scales? and 2) Can evolution still occur in a modern environment?

    Evolution is not the same as speciation, which you seemed to imply in your comment about Silicon Valley engineers . Instead, evolution is simply any measurable change in the relative frequencies of genes in a population (and natural selection is one particular mechanism by which evolution can occur). Given this definition, evolution can in fact occur over the course of a small number of generations, a phenomenon often called ‘microevolution.’ Work on Darwin’s finches by Peter and Rosemary Grant has revealed evolution within the past 30 years, and other work has demonstrated human evolution within a span of 100 years or so (pdf here: http://bit.ly/14oR077). So while evolution doesn’t happen on a time-scale of, say, 10 years, it also doesn’t necessarily require thousands or millions of generations.

    I agree with you that modern medicine has changed the selection pressures that people face and altered the calculus of reproduction, but I don’t agree that the end result is a stasis in evolution. Even if all gene variants are equally fit (lead to identical reproductive success), there is still some chance that a variant spreads and becomes dominant in the population (purely due to random means, like getting 100 heads in a row in coin flips), which is known as genetic drift. Sexual selection is another means by which evolution could happen in the absence of external selection pressures.

    I think one aspect of modern life that has important implications for human evolution is our ability to traverse large distances quickly. Because of this, the entire planet is slowly becoming a single population, as opposed to the geographically localized populations of the past. If the definition of evolution is a change in gene frequencies in the population, then it is harder to reach that criteria if our population is the entire human species. At the same time, we’re creating new variants of humans at a more rapid pace.

  9. thanks for the thoughtful comment! i agree on all points.

    at a high level, you and other commenters are right that i didn’t frame the initial question well enough. i was responding to the idea that we’re physiologically evolving specifically in response to technology and other parts of modern life, which is pretty clearly wrong, but weaker variations like microevolution and genetic drift are still happening.

    you’re also right that i may not have distinguished the timespan and loss of selection/reproduction counterarguments well enough.

  10. I totally agree with you that people speak about evolution too loosely in relation to modern technology.

    Great blog, by the way!

  11. Very interesting post and comments also. I recently took a MOOC course on Epigenetics taught by Marnie Blewitt. Epigenetics is a sexy subject for those who are not doing research on epogenetics. One thing I learned is there is no clear evidence of epigenetic changes passed on to offspring through gametes in humans. Epigenome is completely wiped out and reprogrammed during sensitive periods (primordial germ cell development and pre- and post-implantation periods).

    If you do see transgenerational epigenetic “inheritance” you must ask (a) are they transmitted transgenerationally, i.e., via gametes, or (b) brought about by mothering style, placenta alteration, newborn nutrition, etc.

    People (particularly, science journalists) are eager to claim true epigenetic inheritance through gametes referring to dutch famine, Overkalix, etc. However, subsequent careful studies did not indicate transgenerational effect of the famine.

    It is surprising that it is epigeneticists that caution about making sexy claims in epigenome inheritance. Others seem to liberally make all sorts of inheritance claims not grounded in solid science.

  12. I cannot think of humans in the previous centuries (>1000 years ago) hitting something constantly like we do on computer keyboards. Evolutionary response takes tens of thousands of years, so obviously we are not equipped to pound the keyboard and not suffer the consequences.

    I have a bad habit of hitting the keyboard harder than it needs to be and occasionally my fingers hurt. I have to remind myself to make it soft and use switch fingers (I am not a typist).

    Whenever we do something that requires applying force or (really, impulse) on parts of body due to technological changes, ask yourself, did my ancestors in may be a different activity have similar force/impulse on the same part of the body? If the answer is no, most likely you are not properly equipped to continue practice. Anyway, even after another ten thousand years, we won’t be equipped to hit the keyboards hard since that type of activity is not going to affect “fitness” (in terms of being able to reproduce) and will not seek evolutionary response.

    Perhaps, touchscreens are better than keyboards for this reason.

    This reasoning applies to many other things, like the food we eat. Lactose intolerance is a result of exactly this reason. Humans started consuming cow’s milk only about 5000 years ago and a lot of human populations have not yet adapted their biology to milk.

    How about sitting for long periods of time in front of a computer? What does it do your spine, eyes?

    What about things our ancestors did but we don’t like running or chewing meat (I don’t advocate meat eating)? We are capable of doing these things evolutionarily but if we don’t use it we lose it.

    People in India stand near the door holding onto the bar and precariously hanging out. From physics point of view evolutionarily this seems like the perfect thing we can do (visualize our ancestors, apes doing this on a tree branch).

  13. thanks for the thoughtful comments, soma! and especially for the correction that epigenetics aren’t inherited after all, at least as far as we know. much appreciated!

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