A common riff on the role of medical and technological advances is that they have somehow insulated humanity from evolution, or the ordinary course of evolution. This is an old canard - it goes back to the days before Darwin, and is a basic justification of eugenics programs (not just the Nazi horrors, but the more “positive” programs of encouraging the “better” kind of humans to interbreed).
It is thought that if medicine has interfered with the selective pressures we faced in the past, we will face degeneration, or be in control of our own evolution, or something, that will interfere with the “normal” course of evolution.
A [url = http://www.prospect-magazine.co.uk/ArticleView.asp…]very nice article[/url] by Gabrielle Walker in Prospect Magazine, a UK publication of The Independent, discusses this in some detail.
15 Comments
Reed A. Cartwright · 12 July 2004
Fertility selection is still very active.
John Wilkins · 12 July 2004
How do you mean?
Reed A. Cartwright · 12 July 2004
Well, no matter how well technology has allowed us to resist viability selection, selection on how well we can reproduce is still very active. Most people when that say that "we have stopped evolving" only think of viability selection and not fertility selection. Although modern science has techniques to address infertility, they really don't even the playing field.
John Wilkins · 12 July 2004
Yes indeed. And even if we attend to viability because of one set of pressures (say, if we could prevent deaths from all diseases) there would still be viability pressures of other kinds (violence, car deaths, drug deaths, etc.). Messy buggers, humans...
IXLNXS · 12 July 2004
Look Maw! No pinky toes.
PZ Myers · 12 July 2004
Jim Harrison · 12 July 2004
50.000 year-old human skull look pretty much like modern ones, but I don't think we've got much evidence as to how much genetic change has occurred over the same period. Is there any real evidence that cultural evolution has somehow ends biological evolution? Indeed, why would anybody think it has? Arguably the emergence of culture creates a huge selection pressure for increased brain power since it multiplies the value of intelligence. Living in cities in a cosmopolitan world and exposed to a planet-full of disease germs may also increase the selection pressure for an improved immune system.
PZ Myers · 12 July 2004
John Wilkins · 12 July 2004
The article is useful because it covers the range of opinion - it's reportage rather than advocacy (and yes, it is very annoying yet again to find that someone 74 years after Fisher opened his book with "Natural Selection is not Evolution" still thinks the two ideas are identical). I expect it from Steve Jones. I don't from Alexei Kondrashov...
On the relaxation of selection (if that is, indeed, possible for all aspects of humans), in such a case we simply have a random elimination of alleles when carrying capacity is reached. But if carrying capacity is reached and there are differences in the distributions of resources, then selection will apply. In the interim, though, we might find a faster evolutionary rate, depending on where and for whom. Sudanese children are subjected to a rather different distribution of resources than Minnesotans...
Mr George · 13 July 2004
Lets not forget that a significant portion of people on Earth don't live in western opulence with ample food, clean water and medicine. There will still be selective pressure on people living in third world conditions for things like disease resistance. Claims of immunity to the HIV virus in Africa spring to mind.
Russell · 13 July 2004
Claims of immunity to the HIV virus in Africa spring to mind.
The human genome is littered with retroviral inserts. It's likely that these derive from ancient retroviral plagues where incorporation of the viral genome into the germline of the survivors' lineages rendered them resistant to "infection from without". I wonder if - assuming we humans have any surviving descendants a million years hence - our descendants will have incorporated the HIV genome.
David Harmon · 14 July 2004
Not all populations are "evolving" in the same direction! As noted above, there are very different pressures on different continents and smaller segments.
It's a rough world these days, with a variety of *heavy* selection pressures. Whole races and subraces are being wiped out, or nearly so. For example:
In just 500 years, the various aboriginals native to North and South America have been smashed into a few remnant populations, and a reddish streak in various mixed-race underclasses. In fact, aboriginals in general are doing poorly.
Africa as a whole is experiencing a major die-off, not entirely due to AIDS. Older diseases and climactic changes are also involved here. Asia is teetering at the edge of a similar die-off. On the other hand, the survivors should be a hardier bunch, with widespread immunity to AIDS and perhaps some other diseases.
The industrial nations are getting hit with milder but broad problems related to pollution, pesticide misuse, and a developing stream of drug-resistant diseases, aggravated by poor leadership in the USA.
At the same time, some things don't change. The species has gained noticably in height even since, say, Roman times. Since height is still considered desirable, there seems no reason to expect this to stop. Large breasts are likewise popular, so they will likely continue to gain "share" throughout the species. Health, fertility, and social status will remain the major draws.
The growing UV flux from the ozone layer will probably favor darker-skinned types, individuals with better cancer resistance, and possibly innovative traits. Global warming will likewise favor heat-adaptive sorts. (thinner build, etc.)
Socially-adaptive evolution will likewise continue. There are still large populations with little ability to recognize other tribes as "human". These will continue to get clobbered by groups that can organize larger forces and projects, because they're more willing to work with outsiders. (The story of civilization continues....)
In industrialized areas, there will be (continuing) selection pressure for various technology-related traits; the cognitive abilities underlying literacy and numeracy, manual dexterity, etc. There will *also* be ongoing selection for resistance to various sorts of pollution, from heavy metals to artificial estrogens. As implied above, infectious-disease resistance will also be "coming back into fashion".
The advent of somatic-cell genetic therapy will act like other medical treatments, weakening the selection pressure exerted by treatable conditions. However, when germ-line therapy comes along, that will overwhelm those medical effects, for any treatable gene. (GLT lets us actually remove the offending genes themselves, rather than the individuals bearing them!)
I'm sure others can find other points...Flint · 28 September 2004
Methinks we are pretending to discuss a forest, but our noses are pressed against the bark of a single tree. We are bounded in a nutshell and count ourselves kings of infinite space.
Gould observed in his book The Massive Doorstop of Evolution that certain lineages tend to speciate at a high rate; others almost never. Primates fall in the "almost never" group. Furthermore, speciation is at least plausibly speculated to occur among isolated small populations on the periphery of the territory of the species, but humans are found in more of the planet's territory than anything else (perhaps in a tie with roaches and rats we bring along?) We are not isolated geographically or genetically; humans have interbred lustily throughout all known history, and accelerating mobility has only boosted the rate. The conditions for a branching event are as poorly met by humans as can be imagined.
Maybe I'm unable to grasp the sheer pace of scientific progress, but I doubt we'll generate any new human species (or defy the stasis of equilibrium our circumstances require) through genetic engineering and horizontal gene transfers either. We're a LONG way from engineering "superman saltations" or whatever.
The evidence on the ground argues against the kind of genetic directional change David Harmon describes. Paleontologists "watched" with fascination the life forms abundant on the warm, damp, sea-level territory as (over 15 million years) that territory moved North, rose thousands of feet, and dried to the desert of what is now Wyoming. And did these life forms migrate genetically to the changing adaptive peaks? No, they did not. Those which could tolerate the change did so; those that could not went extinct. Neither group underwent gradual adaptive change. Granted, there were still speciation events and the newly branched species were better suited to the changing environment. But the pioneers never varied. Whatever it is that enforces the Eek part of PunkEek is immensely influential. There is no reason humans should be any exception, even if the above conditions (found planetwide and interbreed everywhere) didn't apply.
As a Proper Darwinian, I predict that IF small colonies of humans populate habitable planets elsewhere in our local spiral arm or wherever, THEN we will see evolution with a vengeance. But PunkEek is a Goldilocks-type observation. The branching group can't be too large (or the statis factor will rule), nor too small (and succumb to inbreeding) nor interact too freely with the main population. Conditions must be Just Right. Colonizing Mars, and then the colony losing contact with Earth for 10,000 generations, should do the trick. IF our models are accurate.
Great White Wonder · 28 September 2004
Flint writes
Another evolutionary kick in the seat would be something like this, except it doesn't miss ...
http://www.cnn.com/2004/TECH/space/09/28/asteriod.fly/index.html
SPACE.com -- The largest asteroid ever known to pass near Earth is making a close celestial brush with the planet this week in an event that professional and backyard astronomers are watching closely.
The space rock, named Toutatis, will not hit Earth, despite rumors of possible doom that have circulated the Internet for months. Humanity is very fortunate there won't be an impact, as the asteroid is large enough to cause global devastation. Toutatis is about 2.9 miles long and 1.5 miles wide (4.6 by 2.4 kilometers).
On September 29, Toutatis will be within a million miles of Earth, or about four times the distance to the Moon.
....
Flint · 28 September 2004
GWW:
Hello again. I agree with you with what I hope are the usual caveats: That some humans survive, that they do so in small isolated populations, that the environments these populations inhabit are hostile but not fatally so, and that these populations remain isolated for enough generations for selection to have significant influence on them.
Frankly, this future holds little appeal for me; I think I'd prefer to be at ground zero...