We are still evolving

ResearchBlogging.orgI participated in a school play when I was 10 years old which opened with the following lyrics

Evolution;
Evolution;
Make and fix and mend;
But now it’s at an end;
Evolution!

The sentiment conveyed in this song is a common one. Evolution, according to most, no longer affects us. No doubt you’ve read something talking about how humanity has removed itself from the natural world to such an extent that we are no longer evolving.

Such statements are typically incorporated into some kind of rant about the evils of humans. About how we’ve divorced ourselves from what is good and natural so much that not even evolution can touch us now.

I wish he looked more evil in this picture

I find their lack of faith disturbing

On the surface this idea seems to make sense: over the past few thousand years we’ve been effortlessly working to not die malnourished on some ratty bit of grassland. A noble goal, in my opinion.

This has turned humans into experts at niche construction (the sciency word for organisms which create their own environment) and if we’re building our own niches then why do we have to adapt? We can just keep things ticking comfortably along the way we like them.

And this does seem to be the case. A disease tries to kill us, we set doctors on it. We feel peckish, we head down to the local supermarket. A lion runs at us, we shoot it. We get cold, we were an undershirt…the list goes on. Every time evolution tries to point out we have no right having 7 billion members of our species sprawled across the globe, we punch it in the metaphorical face.

We work to maintain a stasis whereby we remain alive and happy, regardless of the environment.

Our ancestors smell, we build an extra rung on the tree of life

However, whilst ostensibly valid this logic runs into a pretty critical flaw: we don’t keep things the same. Humans now occupy more extreme territories than they have at any point in the past, from the Antarctic to Space, in larger groups than at any point in the past, with a different diet to at any point in the past.

This is the premise of inceptive niche construction and is an aspect of our technological advancement that is frequently overlooked. Basically, it is pointing out that changing our habitat can create new environments or allow us to inhabit previously unaccessible ones.

Before we developed sufficiently advanced technology we would’ve been inhabiting a rather different environment than we do today. Even after removing various selection pressures – suh as diseases and lions, as previously mentioned – we’re still living in a drastically different environment to the one we would typically be in.

But of course we are also generalists, able to survive quite well in a large variety of environments. Perhaps our new environment, despite being different to the African Savannah our species grew up in, is still within our tolerance and we do not have to evolve after all.

Thus the question becomes whether the selection pressure we create by using out technology to create/survive in new environment are sufficient to drive evolution forwards.

Witty comment unavailible

And the answer to that question seems to be yes! There are examples where recent inceptive niche construction has brought about evolution in Homo sapiens very recently.

All in all, it would seem around 13% of our genome is currently under selection pressures*. So, whilst we may be living in a seemingly artifical environment we have yet to escape the natural process of evolution.

Evolution;
Evolution;
Make and fix and mend;
It’s not yet at an end;
Evolution!

Laland, K., Odling-Smee, J., & Feldman, M. (2000). Niche construction, biological evolution, and cultural change Behavioral and Brain Sciences, 23 (1), 131-146 DOI: 10.1017/S0140525X00002417

*That does include “purifying selection” where evolution removes deliterious mutations. But ultimatley that is still evolution in action, even if it is not moving us forwards.

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11 thoughts on “We are still evolving

    • Well I have a google alert out on human evolution to pick out interesting things about the subject, so I see it fairly often. But perhaps that’s because I’m looking for it and in reality it isn’t as widespread as I thought. That’s an especially likely scenario given most of the discussions saying human evolution has ground to a halt comes from Yahoo Answers…

      Regardless, I hope you found it interesting.

  1. What actually counts as evolution anyway? Is it just a change in body function, or does it specify a change in genes/gene activation? I ask because it strikes me that things like a change in the age of menopause could be down to a lot of complicated environmental factors ushered in by technology without a change in how our bodies work on a fundamental level.

    • Last time I checked, evolution was technically a change in allele frequencies over time. In that regards mere alteration due to our environment would not count, there must be some actual genetic change. Thus if the changes to menopause are due to environment it would not be evolution. However, their statistical analysis did seem to detect natural selection at work, although I don’t know enough about such analyses to determine if it rules out environmental effects.

  2. There’s a huge difference between “currently under selective pressure” and stochastic genetic drift acting on alleles that were under selective pressure only a few generations ago. I know that several authors have addressed this very problem, but I think that attributing any significant selective pressure to modern human populations in the developed world is grossly overstating the evidence.

    • True; the 13% figure is a revision and will likely be subject to futher alteration. Ultimatley, however, there are examples of inceptive niche construction prompting recent human evolution and there’s no reason to think that won’t continue to be the case. Our increasing use of artificial lighting, for example, might prompt a decrease in eye size (which is currently correlated with light levels, with increasing eye size compensating for decreased light)

  3. One should keep separate the notions of directional selection and stabilizing selection when thinking about whether we’re currently under selective pressure. Sometimes stabilizing selection can get hidden in the data since any variation could be masked by other swamping factors. For instance, human males are probably not under any strong current directional selection pressure for having an orgasm response to intercourse; I’d feel confident in saying that we’re probably at the 99.99% peak already. But I’d also say that we’re still under very strong stabilizing pressure to maintain an almost 100% orgasm response to intercourse, but any variation in the response is probably masked by developmental/hormonal pathways that override that genetic variation. So when we go looking for evidence of selection, we probably wouldn’t find any and assume that there’s little or no current (directional) selection pressures operating on the system, but that wouldn’t mean there’s no pressure at all, just no pressure of a directional type.

  4. Yeah that is a risible idea. How about all the fetuses that are aborted, because of some genetic defect. And the Hardy-Weinberg Equilibrium is supposed to be impossible to achieve.
    Love the humorous comments, great job. : )

  5. Pingback: Humans are still evolving: Women are getting shorter « EvoAnth

  6. Pingback: Sir David Attenborough is wrong, humans are still evolving | EvoAnth

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