Objections have been raised to blogs in verse.
I’d counter that: the form is neat and terse,
Well suited to a form of argument
As practiced by our forebears, who were bent
On laying out such things, in fervent hope
Of changing minds. Said Alexander Pope
‘Know then thyself, presume not God to scan;
The proper study of Mankind is Man.’
Which brings me to a Darwin-year debate
In which I’ve been corralled, in abject state
To call the toss on human evolution.
The case is thus: which one of two solutions
Does one prefer? Has evolution ceased,
Or has it, on the other hand, increased?
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I, Editor by Henry Gee
This is the Nature Network and therefore Terribly Extremely Very Serious foothold for Nature Senior Editor Henry Gee. If you want fun and games, visit http://cromercrox.blogspot.com/
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Lines on the Future of Human Evolution
- Date:
- Thursday, 05 Feb ruary 2009 - 12:20 UTC
Andrew Pomiankowski might prefer
To state that change in man is now deferred.
His colleague, Jones, has made an ample case
For stasis in the current human race.
Fathers now are younger than they were,
Thus barring new mutations, once the spur
Of change. And furthermore, those kids whose genes
That killed them long before they reached their teens
Are now surviving longer, so we witness
An increase in their reproductive fitness.My task: to make an argument, instead,
That strategies of stasis are gainsaid,
And more, with change, and lack of random mating,
That evolution is accelerating!
Look first, around, at people you might meet
In shops, in labs, in pubs and in the street.
If you live in London, and your reading
Is The Guardian (see where this is leading?)
You’d think the world is small, a melting pot
Of people from all countries – it is not.
The wider picture of the human world,
Of human reproduction, boy-meets-girl,
Shows that people generally choose
A local partner. They tend not to cruise
The world outside in search of better mates.
A recent study in Nature illustrates
This well: that human genic variation
Corresponds so closely to location
That variations seen in people’s hap-
-lotypes (ahem) are congruent on maps.A second paradigm I find unsound
Is that evolution’s run aground
Because our minds have taken on the yoke
Of adaptation. Science, at one stroke
Has halted evolution in its course.
Innovation, starting with the horse,
The dog, and fire, and tools of every kind,
Writing, language, aids to naked minds,
Have furthered an expansion of our species
So far beyond our native tropic niches
We’ve even set our feet upon the Moon.
Medicine now offers every boon.
Our native ingenuity, our brains
Have freed us from selection’s prison chains.
To this thesis I’d say au contraire
And propose instead a discourse far more fair
Technology’s not frozen us in aspic
But propelled genetic change so drastic
That its scars are seen across the Earth.
I think the major culprit was the birth
Of agriculture, of whose dire results,
Exposure to disease, immune insults
Have wrought profound and thoroughgoing change
To human beings all across their range.
Far from stopping evolution dead
Technology has spurred it, far ahead.A third misunderstanding one descries
In the stasis argument – a guise
Of evolution concrete, as the Shade
Of Death, with cowl and scythe, whose careful grade
Winnows out those unfit human lives.
Evolution is thus personified!
Natural selection’s no such thing.
All one needs in nature is to bring
A measure of genetic variation,
A peck of ‘vironmental vascillation,
And mix with superfluity of young.
That’s it: and yet from such a mixture’s sprung
The riot that is life upon our Earth.
No God, No Death. Simplicity is worth
A thousand million epicycles. That’s why
We’re celebrating Darwin’s careful eye.
From which it should be clear for all to see
That natural selection has no memory,
No past to rue, no plan, no mind, no trend
Except that those with hindsight seek to bend
It to their will, and so extrapolate
Stories of our origin and fate.
Such hubris! It’s as much as I can seek
To organise my diary for next week!
And so, were you to ask me of the course
Of evolution? I’d say bet upon a horse.Last updated: Thursday, 05 Feb 2009 - 12:20 UTC
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Comments
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Anyone who says that evolution can’t be happening because medicine means we all live for so long should be forced to spend a month reading nothing but books on life history theory. By the end of it they might have worked out that fecundity and timing of reproduction are also important.
Technically, to evolve, all we need is some form of differential reproduction – and is someone really telling me some people don’t have more kids than others? That their traits aren’t being passed down more than someone else’s? Who said the traits have to mean living longer? I’m pretty sure the crazy women who just IVF’d herself 8 kids (after already having six) is passing on a lot more to the next generation than I am… whether it’s a good thing or not.
PS I agree, Bob.
I’m one of those who thinks that (directional) evolution is no longer happening in our species, but not because we are living longer than in the past…
My reasoning goes like this: the theory of natural selection says that, if you have an heritable character that gives you an advantage in terms of how your genes will be represented in the next generation (of humans, in these case), then the presence of this character will be gradually propagated in the general population (that is, we will evolve). My problem is that I have serious problems conceiving a single example of this taking place in modern society. Which kind of trait would be selected? (of course, barring harmful traits such as predisposition for genetic diseases, but that doesn’t give you directional evolution anyway). Of course we have genetic variation, and stretching it a little bit one may argue that this may be responsible for how succesful we are perceived to be by the rest of society, or even for how much sex do we have but…also for how many babies do we have? Really? On this age of widespread contraception? I really have trouble thinking of an actual example, but I’ve always been curious to hear arguments from the other side…
Henry: I find your poetry such a drear, but to you sentiments: hear hear!
Our journal discussion group and this
have entry inspired me to write some
pissdiscussion of evolutionary theory.Christie: I think we need more than just differential reproduction to evolve. Genetic/Phenotypic variation and heritability of phenotypic traits start to become pretty important, amongst other things. The long-term fitness of the genes in a mum-o-twelve sorta depends whether (in)fertility or having IVF are heritable traits or not.
Cristian: I married someone from a different country. My wife and I are very rarely ill, with colds or flues or other reproductive preventing ailments, . If we have kids, I can only imagine our beautiful bairns will be some sort of immunocompentent superheores, who will never suffer a sniffle in their delightful lifetimes, regardless of where we live.
Thank you Henry!
I really like the idea that agriculture likely has the greatest impact on our ability to continue to evolve (maybe for the better, maybe not). With the exploding study of epigenetics and the demonstration that food stuffs can alter not just ours but our off-springs epigenetic make-up this could be the real continuing point of “evolution” of humans. The problem really for looking at evolution is how long of a view are you willing to take?
Mike: That’s great for your kids, but do you really believe that if you and your wife would not have been so healthy and disease-free…you would have had MORE kids?
I can see how that may be the case with more serious diseases, and I’m perfectly willing to admit that in those cases natural selection will obviously play a part, but leaving aside those special cases, is there any other example where reproductive output in modern human societies can be directly linked to a particular genetic profile? (actually, it has to be CAUSED by that profile, otherwise it doesn’t work)
“Which kind of trait would be selected?”
Ability to reproduce despite escalating concentrations of environmental toxins in the average human body?
Yeah, OK, you can circumvent some cases of fertility through IVF, but those people will tend to have fewer children than people who reproduce without medical assistance, simply because of the money and time eaten up by each cycle.
Oh, and immunity to the avian flu, of course ;)
I would posit that evolution may not have been subverted by medical triumphs- but is merely in a holding pattern, as it were; awaiting the next great extinction event. We may not be able to see evolution happening before our eyes; evolution is like history- we can only truly perceive it’s course from a distance, looking back to where we came from, we can determine how we got here; but the closer our observation comes to where we currently are, the more muddled our objectivity becomes.
It has been stated that the average human is taller than was the norm even two hundred years ago. Whether this will be determined to be a niche which needed to be filled or is simply an anomaly of the current human socioeconomic condition is something the future bloggers will have to decide.
@Henry- A man’s blog is his castle, far be it from this lowly knave to tell him how to build it. (However, I must note that English castles were drafty, damp old things; made to be laid siege by the military stars of their day. A siege of stars, so to speak;)
@ Bob: Anyone who says that evolution can’t be happening because medicine means we all live for so long should be forced to spend a month reading nothing but books on life history theory. By the end of it they might have worked out that fecundity and timing of reproduction are also important.
Quite – but that works both ways. Steve Jones has used that as an argument for evolution having slowed down. If fathers are, on average, younger than they were, then they will be less likely to accumulate new mutations that can be passed to offspring. I think that argument is specious, because it fails to account for other adjustments to this very change in life-history, such as reproductive fitness and so on.
@ Christie: I’m pretty sure the crazy women who just IVF’d herself 8 kids (after already having six) is passing on a lot more to the next generation than I am… whether it’s a good thing or not.
A well-established feature of life-history strategy is a trade-off between fecundity and longevity. That is, creatures that reproduce sooner, and more often, tend to be those that die sooner. Conversely, creatures that reproduce slowly and late, live longer. This trade-off exists because of natural selection, whih favours creatures living in more dangerous or marginal environments reproducing as soon as possible, else they are killed before they get the chance to pass on their genes.
This has interesting implications for human society. It is now well-established that women who choose to reproduce later in life tend to be those who’ve had a good education, and therefore access to greater wealth and security. In contrast, women who reproduce earlier tend to ocupy lower rungs on the soial ladder. It’s no accident that teenage mothers tend to come from the less well-educated and poorer parts of society. The Whitehall Study shows that socioeconomic status has a significant effect on longevity, and this persists even after retirement.
@ Christian: is there any other example where reproductive output in modern human societies can be directly linked to a particular genetic profile? (actually, it has to be CAUSED by that profile, otherwise it doesn’t work)
I cannot immediately think of a case of a simple trait that is linked directly to more fecundity, but that’s not really the point. Fecundity no doubt has genetic determinants, however, as there does seem to be variation in fecundity. Some women seem never to be able to conceive, no matter how hard they try, whereas others need only to look at a man to become pregnant. However, fecundity is probably governed at least as much by environmental factors connected with life history, as I discussed above in relation to Christie’s point. In the animal world, it is well known that particular features of the reproductive system influence fecundity, especially in species in which there is sperm competition. However, what is more important overall to the persistence of traits in a population is not fecundity, but reproductive fitness — not the number of babies you have, but the proportion of those babies that survive to reproductive age.
@ Craig: you’re welcome. Agriculture has had a marked effect on human fitness, genetics and physiology that we see to this day. See this article by Jared Diamond on why the prevalence of Type II diabetes varies strongly between ethnic groups, and you’ll see why!
@ John: quite so. The closer one looks at evolution, the messier it becomes, which is why predicting the future is pointless, and why evolutionary trends can only be viewed in hindsight. As for my castle – can I use you as a draught excluder?
You mistake my place in this metaphor, ‘nuncle! I stand without, (a conscience-I having no training in the sciences) flinging not hefty boulders against your mighty redoubt; but merely the collected slop of misunderstanding which has puddled in my lowly mind. Yet still I try; for the shite I fling may contain a germ of an idea against which you have no defense. And if it doesn’t perhaps it will encourage your marrows to grow high against de fence. (In truth that last comment weren’t mine; Herr Mendel shouted it from the recesses of my mind- my mind is oft at recess.)
Indeed I am not a part of the august company without (without jobs, apparently)- but should I find myself WITHIN your Castle Blog; I wouldn’t wish to exclude your draught (for your air blows hot my lord- oh lord how it doth blow!); indeed to your conscription I would be a draft dodger!
Isn’t there research on recent human evolution? There is some work by Jonathan Pritchard showing evidence of recent positive selection in humans. Also, Marcus Feldman has done some work on Chinese populations — what, for example, is the evolutionary consequence of the one-child policy? In big Chinese cities, there are 120 boys born for every 100 girls, and this has to have some cultural, societal, and evolutionary consequences…
Viviane: sure, that’s a particularly good example of a recent evolutionary trend in the human lineage. Having the ability to digest lactose was probably very important for primitive agricultural societies, for example to survive periods of famine.
I still think that modern societies are simply getting out of the game, for the following reason: the more we become isolated from the environment, the more we manage to prevent environmental factors from determining who lives, who dies and who reproduces (an this is something that in principle we are striving to achieve), the less likely it is that we’ll see natural selection modifying the genetic background of our species in any particular direction. The conditions for it to work simply won’t be there anymore.
@Viviane; good points. It shows that the assumption that nothing has happened for 100,000 years is wrong. We are still evolving in all kinds of ways.
@Christian; the very fact of our isolation from the environment is itself an evolutionary force, because our technology is a part of the environment, and because people who would otherwise have died young now survive to reproduce – this means that alleles once thought deleterious are now less so, and can spread through the population.
@Christian- another point about ‘direction’: evolution is not inherently directional. That’s something we detect only after the fact.
@Henry -
This assumes that there is little standing genetic variation, though.
@Viviane -
There was a paper recently suggesting that these results (I think it was these results, I should really check though) were artefacts of the analysis, and could be explained by biased DNA repair (commentary here).
Bob – I think that’s Steve Jones’ argument. It won’t work, though, as you say, because genetic variation is enormous. Not so much standing as jumping enthusiastically up and down.
Cristian & Henry: I echo Henry’s point about “isolation from the environment”. Wherever we exist is our environment. Even if it’s a climatically controlled growth chamber, our adaptiveness (or fitness) is still relative to this environment. We can’t really isolate ourselves from whatever environment we find ourselves in.
There is also a hint of an implicit suggestion that our current “comfortable” environment will persist for the indefinite future, thus slowing down evolution, or grinding it to a halt. History suggests that will not be the case. Our environment is gloriously and constantly changing!
Exactly. And as the environment changes, so do we – and that environment includes our own technology.
Mike & Henry: Of course technology modifies our environment, I couldn’t agree more with that. However, what I’m saying is that this (an environment) is not the only condition required for natural selection to happen: you also need this environment (however it may be) to actually determine your reproductive output (roughly speaking, who lives and who dies, and how many kids those who live leave behind after they eventually die too) based on your genotype, and this is what I don’t see happening under our current “confortable” environment (to use Mike’s words).
Granted, there is no asurance that this will persist in the future. If we start fighting each other for food and resources again (let’s call it a “Mad Max/28 days later/Planet of the Apes” scenario) , I’m sure that natural selection would come back in full swing, but whether this would happen (and when) is completely uncertain at this point. How low does the interest rates have to get before we drop all pretenses of civilization? That’s the question…