There's so much wrong with this article by Steve Jones that I don't know where to begin. So I'll leave it up to Sandwalk readers to comment. Steve Jones is a Professor of genetics at University College, London (UK) and the author of Darwin's Ghost.From Times Online via RichardDawkins.net.
Be sure to keep in mind the definition of evolution [What Is Evolution?].Leading geneticist Steve Jones says human evolution is over
By Julia Belluz
Human evolution is grinding to a halt because of a shortage of older fathers in the West, according to a leading genetics expert.
Fathers over the age of 35 are more likely to pass on mutations, according to Professor Steve Jones, of University College London.
Speaking today at a UCL lecture entitled "Human evolution is over" Professor Jones will argue that there were three components to evolution – natural selection, mutation and random change. "Quite unexpectedly, we have dropped the human mutation rate because of a change in reproductive patterns," Professor Jones told The Times.
"Human social change often changes our genetic future," he said, citing marriage patterns and contraception as examples. Although chemicals and radioactive pollution could alter genetics, one of the most important mutation triggers is advanced age in men.
This is because cell divisions in males increase with age. "Every time there is a cell division, there is a chance of a mistake, a mutation, an error," he said. "For a 29-year old father [the mean age of reproduction in the West] there are around 300 divisions between the sperm that made him and the one he passes on – each one with an opportunity to make mistakes.
"For a 50-year-old father, the figure is well over a thousand. A drop in the number of older fathers will thus have a major effect on the rate of mutation."
Professor Jones added: "In the old days, you would find one powerful man having hundreds of children." He cites the fecund Moulay Ismail of Morocco, who died in the 18th century, and is reputed to have fathered 888 children. To achieve this feat, Ismail is thought to have copulated with an average of about 1.2 women a day over 60 years.
Another factor is the weakening of natural selection. "In ancient times half our children would have died by the age of 20. Now, in the Western world, 98 per cent of them are surviving to 21."
Decreasing randomness is another contributing factor. "Humans are 10,000 times more common than we should be, according to the rules of the animal kingdom, and we have agriculture to thank for that. Without farming, the world population would probably have reached half a million by now – about the size of the population of Glasgow.
"Small populations which are isolated can evolve at random as genes are accidentally lost. World-wide, all populations are becoming connected and the opportunity for random change is dwindling. History is made in bed, but nowadays the beds are getting closer together. We are mixing into a glo-bal mass, and the future is brown."
Shouldn't a professor of genetics know that natural selection is a BRAKE on evolution?
ReplyDeleteHe writes: "In ancient times half our children would have died by the age of 20. Now, in the Western world, 98 per cent of them are surviving to 21."
Exactly. Which means that the diversity of the human gene pool is INCREASING (what was the definition of evolution again???)! Alleles that would have once led to lack of reproductive fitness are now being passed on because medical science has improved the survival chances of individuals possessing these mutations. Those that were once "unfit", to use the common (and incorrect) vernacular, have become "fit"; the selection pressure has been lifted.
Natural selection can only limit evolution; if all genotypes were compatible with survival, selection would have exactly zero effect, and evolution would be maximized.
It seems the good professor has confused real, unguided evolution with the teleologic, public (mis)conception of evolution in which the weak are supplanted by the strong, and the ultimate goal, as it were, of evolution, was biological "perfection".
For shame.
As you say, there are many, many issues with this article 'decreasing randomness' (I assume he means less effect of genetic drift)? However, perhaps Dr. Jones should spend some time thinking about average life expectancy before the 20th century. If older men are supposedly responsible 'for' evolution, then there must not have been much evolution before the advent of modern medecine...
ReplyDeleteWow, my head hurts. Under his rational we must not have evolved much upto 300BC or so; which is approximately when the average human life expectancy hit 30.
ReplyDeleteAnd he must also be ignoring some of the rather dramatic recent examples of natural selection acting in human populations, such as the HLA-A*6802 and HLA-B18 alleles, which have recently become enriched in some African subpopulations because they provide resistance to HIV.
And, as others have already mentioned, he's ignoring all of that evolution which goes along just fine without natural selection - drift and all that...
Wow. That was odd. It's very unfortunate he got that into the press. Undoing that sort of public misconception will be quite difficult.
ReplyDeleteI would like to see him explain mitochondrial evolution, if older men are responsible for it all ;-)
ignoring all of that evolution which goes along just fine without natural selection
ReplyDeleteIn fact, evolution always goes along better without selection; selection limits the change in genotypes over time (to those genotypes which are reproductively favoured by the current set of selection pressures), which is the definition of evolution.
While selection guides evolution (once again, in the direction that is favoured by the set of selection pressures), it also slows evolution. There is no getting around the fact that as we increase the number of genotypes that are compatible with human survival (through medicine, for instance), we are increasing the rate of evolution, not decreasing it.
The good professor has it exactly backward.
What what what? This is rather silly. It should be blindingly obvious that with the human population ballooning, mutations are going to get incorporated at an elevated rate. This is how we detect signals of past population explosions in many species!
ReplyDeleteThough, I would expect as humans become more mobile (and more panmictic), and the population increase, drift will take a lesser role in human evolution. Similary, adaptive evolution might slow a bit (because of the aforementioned mobility, there's very little `environmental consensus` between generations).
But, since drift and natural selection (except in rare instance) tends to decrease diversity, we should see a bouquet of novel alleles both now and in our future.
It would be interesting if per-generation mutation rates had indeed changed in a measureable way in a single large-bodied-mammal species over last 200 years or so. Does the good professor provide evidence that this has occurred, beyond the rather fragile chain of reasoning present in his argument about fathers' ages?
ReplyDeleteI especially like the little stab at the end - watch out for all those brown people! They're what happen when you stop evolving! Did the professor actually say that, or did someone at the newspaper slip that in?
I wonder how such a well known scientist write such a crap and get away with it. There are many out there who are publishing a lot of scientific papers these days even though they have no or less knowledge. I like to see a well qualified students to get their PhD rather than anyone who has a MS degree.
ReplyDelete"if all genotypes were compatible with survival, selection would have exactly zero effect"
ReplyDeleteNo, because natural selection is differential reproduction (not survival) of genotypes. You can have the carriers of all genotypes equally surviving, but having very different number of childs.
", and evolution would be maximized"
In a big population, without selection, evoltion is NOT "maximized".
Sounds more like a ploy to increase sales by fabricating a controversy.
ReplyDeleteJones, - another of Koestler's 'Call Girls'?
Im surprised that Steve Jones would come out with such a silly argument.
ReplyDeleteThe improvement in healthcare worldwide has resulted in a drop in the levels of negative selection that existed previously. At the same time, however it has resulted in an increase in positive selection in individuals who simply reproduce more in general.
The only way human evolution could end is if we managed to work out how to effectively clone people and stuck with that Brave New World scenario, with only a single genotype allowable.
When I first saw the press release and hit the words "Natural Selection" I thought to myself "I bet Larry's commenting on this one!" So over I came to Sandwalk and guess what?
ReplyDeleteMy second thought was: Do I really think I understand evolution better than a professor of genetics?
martinc said: I'm surprised that Steve Jones would come out with such a silly argument.
ReplyDeleteI'm not actually all that surprised, because this argument reminds me a lot of things he said in his book Y: The Descent of Men, (http://www.amazon.com/Y-Descent-Men-Steve-Jones/dp/0618565612/) where he argued that the tendency of Y chromosomes to lose genes over evolutionary time meant that men would eventually disappear.
As I commented at Amazon, "More seriously, the whole book encourages a confusion between maleness and possession of a Y chromosome, even though the author is perfectly well aware (and explains in the first chapter) that the system for sex determination used by most mammals is only one of several that exist in nature. The Y chromosome is slowly losing genes, and may conceivably retain none at all after some more millions of years of evolution, but so what? There is no necessary implication that the male sex will disappear and that humans will adopt parthenogenesis."
Stephen Haines, whose Amazon reviews on evolution books are in general very reliable, liked the book a lot more than I did. Maybe he was right, but in general I have always found Steve Jones over-rated as a writer.
No, because natural selection is differential reproduction (not survival) of genotypes. You can have the carriers of all genotypes equally surviving, but having very different number of childs.
ReplyDeleteQuite right. But if we remove selection pressures (i.e. through medical interventions), we increase the reproductive capacity of everyone, irrespective of genotype.
Natural selection is a brake on evolution; it can only slow the rate of evolution, because it leads to loss of genotype diversity by elimination of alleles that are incompatible with particular selection pressures.
What selection DOES do is guide evolution; it is the "non-random" in "evolution is a non-random process" (insofar as that is true...). But evolution procedes faster when selection pressures are removed.
"Quite right. But if we remove selection pressures (i.e. through medical interventions), we increase the reproductive capacity of everyone, irrespective of genotype."
ReplyDeleteIf we remove all selection pressures, all genotypes can reproduce equal, of course... by definition.
But I can't see why medical interventions would increase the reproduction of *all* genotypes exactly in the same proportion.
"Natural selection is a brake on evolution; it can only slow the rate of evolution, because it leads to loss of genotype diversity by elimination of alleles that are incompatible with particular selection pressures."
But genotype diversity is not evolution. Evolution is change in genotype frequencies. Fast evolution is fast change in the frequencies, even if it leads to low diversity.
And natural selection is not only the elimination of "incompatible" alleles. It is also the spread of better reproducing genotypes. It's a matter of degree, not a black or white, compatible/incompatible thing.
"But evolution procedes faster when selection pressures are removed"
Or not. It could be faster, it could be slower. I depends on several factors. Intense positive selection in a medium or big population can produce very very fast evolution, for example.
Shimomura has just won the Nobel for GSP research. What did he do?
ReplyDeleteIf he did not inject GSP, how did it bind. Is it because it is a protein, it binded inside the cell?
Sorry, that's GFP not GSP
ReplyDeleteGeorge in Oregon
ReplyDeleteI suppose when life expectancy was in the 40's. The "older" fathers of the day had more mutations - because after all its probably all just relative - maybe a bit like dogs years or something....
I think any discussion of life expectancy is pretty useless without acknowledging what life expectancy actually means.
ReplyDeleteIf average life expectancy in some population is 50 years, that does not mean most people can expect to die at age 50. For one thing, we know nothing about the variance around that mean - if the variance is high, perhaps because there are a great many different common ways that people can die, then the average is almost meaningless.
In real populations, the variance does tend to be quite high, because life can end from such a wide range of causes. Another strong effect on the mean life expectancy is infant mortality. One's life expectancy might be very much higher if one survives to 5 years of age, in a population with high infant mortality.
Ancient populations with life expectancies in the 30s probably had very high infant mortality, very high variance in male reproductive success, and very high variance in life expectancy estimated from most ages. So it does not necessarily follow that in a population with a life expectancy of 30 all fathers must be quite young - it's entirely possible that most fathers have very large families, that only a few males born in any single year actually successfuly mate and reproduce, and that most fathers are therefore considerably older than the average age of the population as a whole.
Having said all that, Dr. Jones' comments are still silly.
Disappointing garbage from Jones. Such an astounding claim requires hefty qualification if it's not to decimate the claimer's credibility. But I guess he feels he has nothing left to prove and in the short-term, controversy can only be good for book sales.
ReplyDelete