From our American correspondent, Esteban:
In a recent article here at CT, Tim Worstall himself noted something interesting about human reproduction. During times of severe stress (famine, war, etc.) the ratio of female to male births increases dramatically. Biologists believe this is because the womb (not consciously, of course) changes what pregnancies continue.
This struck me as something rather difficult to ascribe to random chance/natural selection. We all got the grade school lecture about how tall giraffes won the genetic lottery and that’s certainly easy to accept. But, in the example above, human wombs that are capable of this type of “discretion”, “intelligence”, “self-awareness” – that’s rather a tall order. How did the original “smart wombs” get that way?
I’m a bit agnostic about this theory of Intelligent Design, but I do find it intriguing in a few ways. For one, I’ve noticed that people who don’t take it seriously will often use language that sounds supportive (unless they’re on guard to avoid it). For example, we recently attended a wild bird presentation (vultures, hawks, owls, etc.) and the bird wrangler was describing a large owl. He noted that the owl’s feathers were designed differently from a hawk’s due their hunting styles. Note the word “designed” – he didn’t mean it literally, but the aerodynamic qualities are such that unless you make it a point to avoid such language you’re probably going to do so.
Another example – I’ve often heard people try to explain the purpose of the human appendix. Doesn’t “purpose” imply design, not just random variation?
A libertarian economist I read fairly often once noted that he found it interesting that many people on the political left who believe in natural selection without any kind of guidance cannot accept the idea that economical order can arise without their guidance. And, likewise, many on the right are completely comfortable with spontaneous order in free markets but can’t conceive of it in the natural world.
It seems to me that this is a bit like the old “irresistible force versus immovable object” paradox. On the one hand, the universe, life, human life, seem impossibly complex to have happened randomly. On the other hand, the universe is actually very large. Perhaps there are enough monkeys banging away at typewriters to produce not just Shakespeare, but the script of every Seinfeld episode.
There’s an old parable about old two friends who sat up late debating the existence of God. In the morning the Atheist got a cup of coffee and wandered into the study where he found a beautiful poem written in dramatic script. He showed it to his friend and asked when he wrote it. He denied authorship and explained that the cat often sat on the desk watching the birds outside. It must have knocked the top off the inkwell and dragged its tail across the paper, writing the poem accidentally. When the Atheist scoffed at this he was asked “so you believe the whole World just happened by accident, but this poem had to have an author?”
But, back to what got me started – if one accepts the theory above about “smart wombs” it seems like a large leap of faith is necessary not to ascribe some type of direction here. And, as I noted above, unless they make an effort to parse their language very carefully, people will use terms like “designed” regularly regarding evolution, natural selection, biology, etc. (i.e., the human iris is designed to control the amount of light which reaches the retina). Perhaps it’s just that natural selection works like the “invisible hand” and looks so much like an intelligent designer that that terminology feels right?
One final note, in the opening paragraph I included the phrase “not consciously, of course” because Tim used it in his original comment. Not one to miss a trick, he is.
Why would this be a leap? Unless I’m missing something obvious, there seem any number of credible reasons why natural selection might have evolved this behaviour in mammals.
I think the “leap” is believing a womb figured out that “I’d better have female offspring”.
It’s not a leap, simply natural selection. Wombs that produced more female offspring at times of stress left more descendants than those that did not. So those wombs are now more common. Pretty simple stuff.
I am totally sold on Natural Selection, and Earth has been a huge and long-running laboratory with plenty of cosmic rays to induce mutation. The only baffling thing is why the human genome is so coherent and so overwhelmingly useful. The appendix and tailbone are the only pieces that seem truly vestigial. Why wouldn’t, sometimes, a mutation that gives us this ability to change sex ratios during famines, not have screwed up some other useful attribute, or introduced more truly random attributes?
It has screwed up some useful attributes. The usefulness of walking upright has screwed with the mechanics of the lower back. The large cranium has screwed with the manageable size and shape of the female pelvis. Binocular vision in a head that undergoes a growth spurt has screwed with efficient focussing.
Yes, good developments have bad mechanical consequences, but that’s not what I’m talking about. Why have evolutionary advances such as large crania not been wedded by random circumstance to other mutations of no seeming utility at all?
Why would they be? And broadly speaking, complex attributes (rather than single proteins) are controlled by many genes, not single genes. Intelligence for example may be controlled by up to 100 genes. And most genes have two copies in humans which may be two different versions.
No, I am not saying that a single mutation would instantly produce both positive and random effects. I’m saying that selection of a subgroup that has gotten a constructive mutation would thereby include individuals with random and destructive mutations. But the modern genome reflects mutations that are overwhelmingly positive and functional.
This is because the individuals with only beneficial mutations survived to reproduce at a higher rate than the individuals with both beneficial and detrimental mutations. Natural selection is shorthand for “random mutation tested by natural selection”. It’s a two-step process, repeated over and over: something new is tried, then it is tested in the crucible of the real world. If it’s successful, it gets to keep trying; if the world finds it wanting the experiment ends there.
propaganda myths. Lower back works well as a shock absorber when used correctly and kept exercised. Female pelvis works well. Examples of poor design are due to illness or defect. Binocular vision messing with efficient focussing ? maybe during parts of adolescence ? References to issue ?
Perhaps it is poor use of English. It should be what is the function, not purpose, of the appendix.
Feathers are formed differently… not designed.
‘Smart wombs’… environmental stress affects hormone production. For example fear triggers fight or flight mechanism by increasing adrenaline output which does all sorts to the body.
But it is the father’s sperm which determines the sex of the infant. Ascribing the choice to the mother’s womb is just another example of the feminization of science.
Isn’t it more likely that the environmental stresses operate on the father, rather than (or as well as) on the mother? It is well-established that “boy” sperms and “girl” sperms have different characteristics, like motility and period of viability.
Some vaginas get drastically more acidic during times of personal stress. This affects sperms and could affect Xs and Ys differently. It could have evolved as a defense against disease vectors.
(Was candidate Todd Akin thinking along these lines in his career-ending remark that women’s bodies resist getting pregnant as a result of a rape?)
A lot of years ago there was an observation that astronauts tended to have daughters, this was put down to stress and IIRC there was a bit of follow up work with men in stressful jobs and there was some correlation. I’m not sure if any serious research has been done but it seems reasonable that if the male population is stressed its likely to cause stress in females, which would support your point. I’m sure the average astronaut’s wife has a fairly stressful time and I know when I was stressed through work my wife also got a bit… Read more »
Very unlikely. Sperm have a very short life and are produced in very large numbers.
So your hypothesis is that males produce X & Y sperm in exactly equal numbers, regardless of the environmental stress on the male? While that sounds unlikely, it is a testable hypothesis. However, please excuse me if I don’t volunteer for the experiment!
I’m not sure why it’s difficult to understand how it happened? Having more female children is an advantage at some times, so a mutation (more probably a series of mutations that gradually increased the effect) that does that leaves more descendants.
There might well have been the opposite – a mutation that meant more male offspring at times of stress. But that was a bad thing so it was out-competed by the good thing. It’s the basis of natural selection, nothing more.
I think this is key. Phrases like natural selection and survival of the fittest appeal to our desire to express things simply and positively. I think nature works negatively, it slaughters the very unfit and selects against the unfit. What’s left looks like it’s been positively selected.
As for Intelligent Design, how did the Intelligent Designer evolve then? He/she had to just appear if he/she didn’t evolve, so he/she is just a God with no creator.
If he/she evolved then you don’t need an Intelligent Designer to explain our evolution.
begging question. Your final semi-statement/assertion is the traditional western definition of Deity. I hope for a more informed set of assertions, not mere propaganda
It’s not a theory, it’s a fact. Two examples being Kangaroos and Pandas reabsorbing if conditions change for worse.
There are 4 possible reasons for this: 1) At times of high stress there is a relative evolutionary advantage in more female births (evolved for); 2) At times of high stress the body changes in a way that is beneficial to survival and accidentally causes more female births but this is not a relative disadvantage (not worth evolving out); 3) The male / female stress relationship is detrimental but inimically linked to another positive trait that outweighs that detriment (evolved for swings outweighing roundabouts); 4) God designed it that way for some reason. If “4” then why. And if there… Read more »
My money is on (2). To return to the initial observation, whether the food source is dying out or the tribe is under attack, why would it be beneficial to produce more females? “Not worth evolving out”…Our scientists discover something about the human condition; they are not Creationists, but turn their attention to explaining its brilliance.
But, again, it seems there are few things in the human genome it is “not worth evolving out” and that most of the randomness I’d expect mutation to cause, have been evolved out. How and why?
Hmm, Richard, your first weak post.
Thing to remember about natural selection is it may benefit species but it operates on single individuals. Or to be more accurate, the offspring of single individuals.
And any evolved characteristic may look highly unlikely but is, in fact, 100% certain. Because you’re looking at it, now.