Will the availability of C-sections give humans bigger brains?

Posted 17 October 2008 by PZ Myers

While Steve Jones might think human evolution has stopped, I have to say that that is impossible. If human technology removes a selective constraint, that doesn't stop evolution — it just opens up a new degree of freedom and allows change to carry us in a novel direction.

One interesting potential example is the availability of relatively safe Cesarean sections. Babies have very big heads that squeeze with only great difficulty through a relatively narrow pelvis, so the relationship in size between head diameter and the diameter of the pelvic opening has been a limitation on human evolution. We know this had to be a factor in our evolution: the average newborn mammal has a cranial capacity that is roughly 50% of the adult size, chimpanzee babies have heads about 40% of the adult size, but human babies have crania that are only 23% of what they will be in adults. While our brains have gotten larger over evolutionary time, they have not gotten proportionally larger in utero, because large-headed babies increase the difficulty of labor and cause increased mortality in childbirth. If childbirth could bypass the pelvic bottleneck, that would allow for fetal heads to grow larger without increasing the risk of killing mother and/or child.

And childbirth is a risky proposition for women; 529,000 die every year from this natural process (although only about 1% of those deaths occur in places where women have access to good, modern medical facilities — hooray for modern medicine). About 8% of those deaths occur from obstructed labor, where the fetus is unable to proceed through the birth canal for various reasons, and these are the kinds of birth problems that can be circumvented by C-sections. In practice, teaching health care workers how to carry out emergency C-sections has been tested in regions in Africa, where it has actually worked well at reducing maternal mortality.

This is the subject of an article by Joseph Walsh in the American Biology Teacher, which suggests that C-sections will have an effect on human evolution.

"Nothing in biology makes sense except in the light of evolution." This was the title of an essay by geneticist Theodosius Dobzhansky writing in 1973. Many causes have been given for the increased Cesarean section rate in developed countries, but biologic evolution has not been one of them. The C-section rate will continue to rise, because the ability to perform a safe C-section has liberated human childbirth from natural selection directed against too small a maternal pelvis and too large a fetal head. Babies will get bigger and pelves will get smaller because there is nothing to prevent it.

The evidence so far is entirely circumstantial, but Walsh makes an interesting case. There are several correlations that imply an effect, but I can't help but think there are alternative explanations that may swamp out any heritable, evolutionary effect. The kinds of evidence he describes are:

A known trend for increasing birth weight in the US, by about 40 g over 18 years in one study. It's there, all right, but these studies don't demonstrate a genetic component to increased size — it could be a consequence of better nutrition and medical care.
An increasing frequency of C-sections. Again, this isn't necessarily genetically based at all, but could be a consequence of fads in medicine, or social factors, such as an increase in the likelihood of medical malpractice suits making doctors more cautious.
Walsh describes a couple of studies that seem to show that cephalopelvic disproportion (small pelvis or large babies or both together) does have a genetic component. So at least it is likely that there are heritable variations in these parameters that could influence the likelihood of obstructed labor.
There is statistical variation in neo-natal mortality that varies with birth weight in a suggestive way. Low birth weight clearly puts infants at risk, and there is an optimum weight around 3600 grams for newborns that minimizes mortality. Death rates also rise with increasing birth weight above the optimum. There is some data that suggest that availablity of modern medical care and C-sections reduces infant mortality at larger birth weights.

That increasing availability of C-sections might lead to an evolutionary shift towards increasing cranial capacity at birth is a reasonable hypothesis, but I'm not convinced that it has been convincingly demonstrated yet. There are too many variables that effect brain size at birth to make a clean analysis possible; in addition, many of the measures are indirect. Often, we use birth weight as a proxy for cranial capacity, and that means the numbers and correlations are sloppier than they should be. Many of the measurements made are of factors that are readily influenced by the environment, which makes it difficult to imply that these are the product of genetics.

So the idea is weakly supported, but tantalizing. Even as a purely theoretical exercise, though, what it does say is that it is obvious that human culture cannot end human evolution…all it can do is shape the direction in which it can occur.

Walsh J (2008) Evolution & the Cesarean Section Rate. The American Biology Teacher 70(7):401-404.

52 Comments

D. P. Robin · 17 October 2008

A very interesting idea. I'd like to turn it on its head so as to speak.

The counterpart to large brains is wide hips in women to support a birth canal through which a baby's head can fit. Rather than removing a problematic constraint on brain size in adults, I'd argue that were there to be universal use of C-sections you have surely removed or at least drastically reduced selective pressure on maintaining wide hip and that pelvic breadth would over time tend back towards males.

(I'll stop here in the interest of time and brevity).

dpr

g · 17 October 2008

I've wondered idly about this from time to time. It worries me a little: suppose that indeed there's no longer substantial selection pressure for wide pelvis and small head, and that over the next while the human population (or substantial portions of it, in countries with good medical facilities) evolves smaller pelves and bigger heads. And suppose, then, there's some kind of short-term crisis that interferes with those good medical facilities: then instead of setting civilization back for a bit, we lose half the population...

Richard Simons · 17 October 2008

Some years ago I was told that there has been a change in the proportion of Rh negative children being born because modern medicine has changed the chances of survival where the mother is Rh-. Is there any data to back this up?

eric · 17 October 2008

Meh, 3 billion people live on less than $3/day. This is not a problem for homo sapiens, its at worst a problem for some individual bloodlines who happen to be comparatively very wealthy. And even that worry is speculative.

Dan · 17 October 2008

On another side, I've heard that children born via C-section have weaker immune systems, so could we also become a frailer people as well? And how would that effect the transfer of genetic material? Interesting thought, at least.

Dale Husband · 17 October 2008

Note that Intelligent Design gets a terrible blow from the facts regarding the human female reproductive system. Instead of babies going out through the narrow and thus dangerous pelvic region, why not have them go out through the abdominal wall NATURALLY? No need for C-sections! Brains of most mammals would be much larger and high intelligence would have evolved sooner and be more common. Animal babies would be much stronger at birth too.

Henry J · 17 October 2008

Four legged mammals don't really have the same problem though, do they? Or is it that just because their heads are comparatively smaller at birth?

Henry

D. P. Robin · 17 October 2008

Dale Husband said: Note that Intelligent Design gets a terrible blow from the facts regarding the human female reproductive system. Instead of babies going out through the narrow and thus dangerous pelvic region, why not have them go out through the abdominal wall NATURALLY? No need for C-sections! Brains of most mammals would be much larger and high intelligence would have evolved sooner and be more common. Animal babies would be much stronger at birth too.

I've thought that it would be just simpler to call it "Design". After all, they have no answer to the problem of organisms being poorly designed from the engineering standpoint. Or maybe they should be call "Irreducible Complexigans"?

Ichthyic · 17 October 2008

Meh, 3 billion people live on less than $3/day. This is not a problem for homo sapiens, its at worst a problem for some individual bloodlines who happen to be comparatively very wealthy. And even that worry is speculative.

*bing*

Paul Burnett · 17 October 2008

Dale Husband said: Instead of babies going out through the narrow and thus dangerous pelvic region, why not have them go out through the abdominal wall NATURALLY?

Marsupials have tried a multi-step variation of this (sort of...) but remain rather low in intelligence.

iml8 · 17 October 2008

D. P. Robin said: After all, they have no answer to the problem of organisms being poorly designed from the engineering standpoint.

Of COURSE they do! "Maybe the Designer was stupid! Maybe he was whimsical! Maybe he was on recreational drugs!" "Try. Again." "Oh, not buying that? Well, OK, maybe there really is a good reason for it, it's actually well designed, we just don't know enough to appreciate it." "Ahhh ... so if it looks like a nice clean design, it's proof of Intelligent Design -- if it doesn't, it still probably IS Intelligently Designed, we just don't know enough to tell! But then again, if we're too clueless to know if something is Intelligently Designed or not, doesn't the ID argument fall over and die? ... oh SILLY ME! Did I phrase that as a QUESTION?" I didn't say they were GOOD answers. White Rabbit (Greg Goebel) http://www.vectorsite.net/gblog.html

Henry J · 17 October 2008

doesn’t the ID argument fall over and die?

Not if it wasn't standing up to start with! ;)

Dale Husband · 17 October 2008

Paul Burnett said:
Dale Husband said: Instead of babies going out through the narrow and thus dangerous pelvic region, why not have them go out through the abdominal wall NATURALLY?
Marsupials have tried a multi-step variation of this (sort of...) but remain rather low in intelligence.

That's because at birth, marsupials must have their bodies and brain power, limited though it is, to concentrate on climbing into their mother's pouch, and they are exposed to disease germs, which also uses up a lot of energy to protect the tiny and undeveloped baby. Brains use up a great deal of energy and natural selection would favor protection of the baby from disease over it being more intelligent, so their brains would grow slower than placental babies' brains. Placentals are more successful because their preganancies are longer, protecting the baby from disease until they are bigger. And since their bodies are bigger at birth, their brains can be bigger, but they are still limited by the mother's pelvic region. Marsupials are also an example of bad design. Why don't they give birth directly into the pouch, instead of outside the pouch and between the female's legs? Indeed, why should marsupials exist at all? So an Intelligent Designer should be expected to make ALL mammals placental and have their vaginas open out the abdominal wall, thus making birth easier for mothers and not limiting brain size for newborns.

DS · 17 October 2008

Actually, cranial dimensions at birth and pelvic size are not the only traits that are affected by relaxed selection. There is evidence to suggest that every human carries the equivalent of 5-6 recessive muations that would be lethal if homozygous. A lot of that variation might be due to relaxed selection. So, if we lost modern medicine for any length of time, the results might indeed be disasterous.

But then again, what are the odds that humans would be stupid enough to let that happen? Surely they wouldn't develop weapons powerful enough to destroy civilization before acquiring the wisdom not to use them.

Thomas · 17 October 2008

On the subject of evolution stopping, with a population as large as human beings, with virtually no limits on our regional and global mobility, genetic drift is essentially eliminated. After selection, drift is arguably the most powerful agent of evolution but the significance of drift is inversely proportional to population.

Moreover, human evolution insomuch as it could lead to speciation has, if not stopped, slowed to such a crawl as to be undetectable even over thousands of generations.

In order for us to speciate we would have to experience some sort of global disaster that drastically reduces the global population or some subset of the population would have to be isolated within a space with different selective pressures than the world at large. In both these cases drift would again become a significant factor in the progression of human evolution.

Ah, punctuated equilibrium in action.

Frank B · 17 October 2008

Richard Simons Said: Some years ago I was told that there has been a change in the proportion of Rh negative children being born

19 percent of the population is Rh Negative. So the chance that an Rh- woman will have an Rh+ spouse is about 80 percent. The chance she will bare an Rh+ child is greater than 50 percent. This is where the risk due to the Rh factor comes in. If the mother's immune system gets exposed to Rh+ cord cells, then she may produce antibodies to the Rh factor (Anti-D). Without modern medicine, the child may die of Hemolytic Disease of the Newborn(HDN). Modern procedures greatly reduce the risk. Rh+ children are the ones at risk, so they will survive in greater numbers. But the ones born of Rh- moms are few. Any affect on the percentages will be very slight.

Crudely Wrott · 17 October 2008

Evolution in humans stopping? Only in humans? Or in some or all species? Or only selected genera? In any case, why?

Guess 1) An evolutionary goal had been reached and selective pressures evaporated. I got what I want. That is, what my ancestors wanted.

Guess 2) An evolutionary goal had been totally broken by behavioral traits. Naughty people thinking well.

Guess 3) Some fundamental quality of the universe suddenly changed. Like f=m*a.

Guess 4) That's the way Dog wants it.

Guess 5) Apparently, from what we currently know, things could have turned out differently but they didn't. They turned out just like this. And there is reason to think that if things had turned out differently, we would still be able to make useful models of it all. Some models exist in the mind, some in computer code and lots of them exist on the backs of cocktail napkins. Interestingly, a great number of models seem to be connected in logical ways. In some cases, models based on previous models can be made that allow you to first make a model of something and then go make the thing out of real matter and energy. Frequently, the thing made is something completely new.

In general, broadly speaking, without resort to any confirming authority beyond what a person can conceive and model--

1) and 2) are easily dismissed. Each assumes that any evolutionary process has a purpose when it is developing and that it is aimed at a target. There are many good arguments against this, not limited to temporal problems.

As for 3), well, it would be hard to miss.

4): Dog bless all believers. Except the shrill and insistent ones. And the ones who kill people who offend their deep religious sensibilities. The remainder are usually hard to tell apart in casual relations and are genuinely nice people. Good neighbors. People of good humor and honesty are a normal occurrence, and some of them just happen to take great comfort in notions that others find either hilarious or threatening. Common among many religions is the notion that our present biological life is just one of two or more lives that we live. So curious are they as to the nature of the next, or final, life, that all manner of speculation and claims of truth abound. They clash with a terrible sound yet out of the noise comes the assumption that this life is worth less, or is only preparatory to, the really big show. This life is the testing ground for future bliss, and so they trade today for tomorrow. The day is then most certainly gone. But bless them anyway. I do. From the bottom of my black, godless heart.

5). Hmmm.

Crudely Wrott · 17 October 2008

I ran OT in my reply to Guess 4 above. Another thread got mixed in. [blush]

I meant to say that the application of our brains, connected as they are to our eyes and ears and hands and such, yields quantitative results. Even when the results are unsuspected and contrary to expectation. We seem to be able to adapt not only over eons, we seem to do it in moments when the unexpected happens. Science is this talent combined with a talent for keeping detailed records. In myriad situations, not only is evolution observable, but also revealed are the details of how it happens. And all this from just paying attention. But we are a long way from predicting how our genetic makeup will settle into a state of equilibrium. To say nothing of the implied control of environment to a severe degree. So any such prediction must be held at arm's length until there is evidence. Prediction fails.

The other Guesses share common variants of anthropomorphism, which is chiefly comprised of projecting human desire onto innate matter. They are also very religious in that each assumes an overriding imperative impose upon reality from without. And they do not yield quantitative results.

Robert · 18 October 2008

Is this right?
We gave up the ability of swift flight, for an upright gate, which freed the hands, but at the cost of a bent spine and necessarily narrower hips, and therefore more undeveloped child at birth, mentally and physically?
Please forgive, if this is obvious, I am an interested ammateur and would enjoy a more rigorous (please brief) instruction.
Rob.
P.S leads to articles and sites are ok, but, a quicky here would be pleasant.

Eric Finn · 18 October 2008

The fossil record indicates increase of cranial volume during the evolution of one branch of primates to modern humans. During the same time, more elaborate tools have been taken in use. In this respect, humans are more intelligent than other primates.

The physical sizes of humans vary quite a lot. So do their cranial volumes (although much less) without any apparent impact on one's intelligence, as we commonly perceive it. Could it be possible that the large head of a human baby is just a by-product of the change that led to improved tool-making?

Regards

Eric

P.S. I refuse to discuss how many neurons are required to be able to build a nuclear bomb.

Torbjörn Larsson, OM · 18 October 2008

Eric Finn said: Could it be possible that the large head of a human baby is just a by-product of the change that led to improved tool-making?

Hmm. As I understand it, the data points to mainly selection for the immune and sexual characteristics. (As when comparing humans to chimps.) So the a priori likelihood [well, technically there isn't such a beast, but you know what I mean, a chain of likelihoods setting] is that a large head is involved in either. (I'm discounting drift which was important for earlier evolution in the historically small populations, but it happened, concurrently even, in several lineages so in my layman eyes it was likely due to selective pressures.) You just pointed out that cranial volume doesn't necessarily tie tightly to intelligence - and it seems to me that anyway humans have used their greater social and technical abilities to build tightly knitted communities where diseases flourish. Remains that a large head is a good basis for an abundant hair growth - and suspiciously hair growth patterns differs a lot between humans and other primates. To think that so many generations of humans have suffered just to allow the Las Vegas era hairdo of The King!

Eric Finn · 18 October 2008

I tend to agree with you.

Torbjörn Larsson, OM said: You just pointed out that cranial volume doesn't necessarily tie tightly to intelligence - and it seems to me that anyway humans have used their greater social and technical abilities to build tightly knitted communities where diseases flourish.

Indeed, it seems that the power of working in groups, where individual efforts may also count, can compensate even for the drawback of having contagious diseases.

Remains that a large head is a good basis for an abundant hair growth - and suspiciously hair growth patterns differs a lot between humans and other primates. To think that so many generations of humans have suffered just to allow the Las Vegas era hairdo of The King!

I think that this is an important observation. Anyway, any given hairdo is easier to change than tattoos on the skin, and hairdos are equally visible. Piercings may convey a message that can not be expressed by hairdo or clothing only. Regards Eric

JGB · 19 October 2008

Just a note on the C-section evidence. If you compare C sections rates in European countries you would quickly note that the American rate is a complete abberration. The evidence is much more in favor of thousands of frivolous C -sections being performed in the United States probably from a few different sociological factors all costing a lot of wasted money.

novparl · 20 October 2008

So why hasn't natural selection selected for easier birth? After all, there've been millions of other selections.

Prof. Jones may be right for the wrong reasons. After all, nothing's evolving at the moment. Except viruses.

Looking forward to the abuse.

Dave Luckett · 20 October 2008

"So why hasn’t natural selection selected for easier birth?"

Because selection pressure for greater intelligence is stronger. There are a number of drawbacks to larger brain size - energy needs, cooling problems, difficult birth (though this is at least partially also attributable to bipedalism) and very long dependent infancy and childhood. But a larger brain makes up for them.

As Clarence Darrow asked, in the Scopes monkey trial, "What else sets us apart from the animals?"

D. P. Robin · 20 October 2008

novparl said: So why hasn't natural selection selected for easier birth? After all, there've been millions of other selections. Prof. Jones may be right for the wrong reasons. After all, nothing's evolving at the moment. Except viruses. Looking forward to the abuse.

Fairly simple. If pelvic size gets too large, mobility is compromised. Remember, that most women need to be mobile--in order to rear children, if nothing else.

Science Avenger · 20 October 2008

novparl said: Prof. Jones may be right for the wrong reasons. After all, nothing's evolving at the moment. Except viruses. Looking forward to the abuse.

Well what do you expect when you say things like that? The only way evolution could stop is if the DNA replication process suddenly became perfect. There's no evidence of that.

fnxtr · 20 October 2008

I get the impression novparl thinks evolution is goal-oriented, that's why he doesn't see any.

I think the issue of variation was addressed earlier... is humanity becoming, er, homogeneous because of the worldwide mobility of much of the population?

Are blood types dispersing geographically?

I wonder what kind variation we'll see in the sapiens population over the next 100 or 1000 years with the removal of so much selection pressure.

What new selection will arise out of social constructs?

Stuart Weinstein · 20 October 2008

Not only bigger brains, but tighter vaginas should also result.

Interesting combination.

novparl · 21 October 2008

@ Science Avenger (aggressive name!) - that's exactly what I expect. Bit disappointed there isn't more abuse.

@ fnxtr - relaxation of selection? With overpopulation pressure? It'll be survival of the fittest - or the strongest, as the Germans say (Ueberlebung der Staerksten).

Stanton · 21 October 2008

Science Avenger said:
novparl said: Prof. Jones may be right for the wrong reasons. After all, nothing's evolving at the moment. Except viruses. Looking forward to the abuse.
Well what do you expect when you say things like that? The only way evolution could stop is if the DNA replication process suddenly became perfect. There's no evidence of that.

The only case where DNA replication is (close to) perfect is when the species in question has converted sexual reproduction into a cloning process, such as Papua New Guinean antplants, whose flowers pollinate themselves before opening to prevent their pollen from being destroyed by their ant symbiotes' anti-fungal secretions, or the hybrid night lizards which have to have their parthenogenesis jumpstarted by going through mating rituals.

novparl said: @ Science Avenger (aggressive name!) - that's exactly what I expect. Bit disappointed there isn't more abuse.

By constantly broadcasting the fact that one of your primary purposes here is to play the martyr, you continually destroy your own credibility and respect, as well as destroy our own ability to trust anything you say.

@ fnxtr - relaxation of selection? With overpopulation pressure? It'll be survival of the fittest - or the strongest, as the Germans say (Ueberlebung der Staerksten).

So name an evolutionary biologist today who advocates using "descent with modification" as a foundation for social policies, please.

Veri Kurtarma · 21 October 2008

"And childbirth is a risky proposition for women; 529,000 die every year from this natural process"
Is this info come from UN?

fnxtr · 21 October 2008

Stanton I hope that was pointed at novparl. I was thinking more about sexual selection and what becomes fashionable from one season to the next, and in what sub-cultures. Maybe there will never be a large enough preference for a certain image of man/woman to influence genetic drift in any particular direction (though Madison Avenue is trying). Or several directions, depending on whose clique you're in. (Or maybe we'll grow big flashy tails ;-} ).

ARN · 21 October 2008

@Article

An increasing frequency of C-sections. Again, this isn't necessarily genetically based at all, but could be a consequence of fads in medicine, or social factors, such as an increase in the likelihood of medical malpractice suits making doctors more cautious.

That, and C-sections means more money for the Doctors. In India, C-sections are becoming common, because Doctors love to charge more money. :)

eric · 21 October 2008

novparl said: Prof. Jones may be right for the wrong reasons. After all, nothing’s evolving at the moment. Except viruses.

and

@ fnxtr - relaxation of selection? With overpopulation pressure? It'll be survival of the fittest - or the strongest, as the Germans say (Ueberlebung der Staerksten).

Novparl, May I offer the helpful suggestion that your position may be more convincing if you don't make contradictory claims in succeeding posts. Either we're evolving or we aren't, but if you are trying to convince us that humans are not evolving yet simultaneously humans are experiencing survival of the fittest due to population pressure, you're going to have a tough row to hoe.

rward · 21 October 2008

Thomas said: On the subject of evolution stopping, with a population as large as human beings, with virtually no limits on our regional and global mobility, genetic drift is essentially eliminated. After selection, drift is arguably the most powerful agent of evolution but the significance of drift is inversely proportional to population. Moreover, human evolution insomuch as it could lead to speciation has, if not stopped, slowed to such a crawl as to be undetectable even over thousands of generations. In order for us to speciate we would have to experience some sort of global disaster that drastically reduces the global population or some subset of the population would have to be isolated within a space with different selective pressures than the world at large. In both these cases drift would again become a significant factor in the progression of human evolution. Ah, punctuated equilibrium in action.

Thomas, you seem to be assuming there are no small isolated human populations. Stochastic processes will still operate in these. They may also be more subject to differential selective pressure. Evolution hasn't stopped in humans, but it may have moved to the suburbs (figuratively speaking).

Stanton · 21 October 2008

fnxtr said: Stanton I hope that was pointed at novparl. I was thinking more about sexual selection and what becomes fashionable from one season to the next, and in what sub-cultures. Maybe there will never be a large enough preference for a certain image of man/woman to influence genetic drift in any particular direction (though Madison Avenue is trying). Or several directions, depending on whose clique you're in. (Or maybe we'll grow big flashy tails ;-} ).

Yes it was directed at the self-professed wannabe martyr, and there's always cosmetic surgery.

novparl · 22 October 2008

The United States of Angry.

Ah, Stanton, I was hoping you'd show up. Didn't you want to get back at me for ridiculing your feminannyism?

I'm not a self-professed wannabe martyr. I just predicted abuse. I'm not a martyr because I choose to come here to make fun of you emotionalists. Boo hoo.

I destroy your ability to trust anything I say? So what? As dear old Bob dylan used to sing, Ya had no faith to lose an ya know it. Respect? Who wants respect from mean-minded conformists like you?

@ Eric. No contradiction. Survival of the fittest means of the strongest. Even some emolutionists reject the idea of instant evolution.

Let me spell it out. I'm not a martyr because your NRA-style rages are so predictable.

Bless you all.

Dave Luckett · 22 October 2008

When someone's lost it this completely, there's no possible response other than pity. Get help. Seriously.

Stanton · 22 October 2008

Dave Luckett said: When someone's lost it this completely, there's no possible response other than pity. Get help. Seriously.

It would help if novparl was sane enough to recognize that he needs help, but...

GvlGeologist, FCD · 22 October 2008

novparl said: The United States of Angry. Ah, Stanton, I was hoping you'd show up. Didn't you want to get back at me for ridiculing your feminannyism? I'm not a self-professed wannabe martyr. I just predicted abuse. I'm not a martyr because I choose to come here to make fun of you emotionalists. Boo hoo. I destroy your ability to trust anything I say? So what? As dear old Bob dylan used to sing, Ya had no faith to lose an ya know it. Respect? Who wants respect from mean-minded conformists like you? @ Eric. No contradiction. Survival of the fittest means of the strongest. Even some emolutionists reject the idea of instant evolution. Let me spell it out. I'm not a martyr because your NRA-style rages are so predictable. Bless you all.

And thus the proof that when he said,

Just curious

he was, indeed, lying.

Science Avenger · 22 October 2008

novparl said: Survival of the fittest means of the strongest.

Uh, no it doesn't. In an evolutionary context, it means some genomes have a higher expected number of offspring than others in their environment, and the cumulative effect of these differences is what manifests itself as evolutionary change. This is why Darwin preferred the term "descent with modification". To revisit my favorite example, take wolves and dogs. Wolves are stronger, but dogs are more fit in an environment dominated by humans.

eric · 22 October 2008

novparl said: @ Eric. No contradiction. Survival of the fittest means of the strongest.

(a) No, it doesn't. Strength is one trait that may impact survival but its not the only one and its not always a survival advantage. If it was, all wolves would look like this: http://www.dailymail.co.uk/news/article-467985/Meet-Incredible-Hulk-Hounds.html (b) You don't see the contradiction in claiming survival of the fittest does not result in descent with modification? Under survival of the fittest you've got some animals outbreeding others (descent) based on varying but inherited traits (modification). What am I missing? Explain to me how you can have differential survival based on a trait like strength NOT result in descent with modification.

Even some emolutionists reject the idea of instant evolution.

As far as I know every 'evolutionist' from Darwin on rejects the idea of "instant evolution." Evolution is a multi-generation process. Did you not know this?

eric · 22 October 2008

Wow, and I didn't even read SA's post before posting. Great minds think alike. Or maybe Novparl would say we were indoctrinated by the same darwinist brainwashing program :)

Novparl the non-martyr · 22 October 2008

What marvellous putdowns! I must be one bad bandido!

GvlGeologist - if you repeat that someone's a LIAR loudly enough, it must be true. Hey - m'beard's on fire!

An example of belief in instant evolution, now largely rejected I believe, (I believed it long ago) - there were great floods so giraffes grew their necks. Another, also ridiculed, the trees were dying so your ancestors stopped swinging thru them and magically learned to walk.

Eric the Red - I'm not interested in explaining "differential survival" because I don't believe in evolution theology any more than in Christian theology. Evolution, like the resurrection, is a theory, not a fact.

Once again, I'm loving the delicious irony of this site being named for the civilized Prof Gould. Surely it should be "Unweaving the Rainbow" or "Mt Improbable".

Science Avenger · 22 October 2008

Poe!

Richard Simons · 22 October 2008

Evolution, like the resurrection, is a theory, not a fact.

No, the resurrection is not a theory. A theory is an explanation for a body of facts and makes testable predictions. Notice that it is facts that contribute to the theory, a theory never grows into a fact. The resurrection is neither an explanation nor testable.

An example of belief in instant evolution, now largely rejected I believe, (I believed it long ago) - there were great floods so giraffes grew their necks. Another, also ridiculed, the trees were dying so your ancestors stopped swinging thru them and magically learned to walk.

I think you just made this up. Please give us a citation to an evolutionary biologist who speculated that these changes happened in a single generation.

eric · 22 October 2008

Novparl the non-martyr said: I'm not interested in explaining "differential survival" because I don't believe in evolution theology any more than in Christian theology. Evolution, like the resurrection, is a theory, not a fact.

Okay, let me rephrase my question. You say survival of the fittest happens but evolution does not. This piques my curiosity. So I am asking you for more information on your position. If only the strong survive, how does the genome of the species not change? How, for Novparl, does survival of the fittest preserve a genome and keep it from changing over generations?

Dale Husband · 24 October 2008

novparl said: Looking forward to the abuse. Bit disappointed there isn't more abuse. I'm not a self-professed wannabe martyr. I just predicted abuse. I'm not a martyr because I choose to come here to make fun of you emotionalists. Boo hoo. I destroy your ability to trust anything I say? So what? As dear old Bob dylan used to sing, Ya had no faith to lose an ya know it. Respect? Who wants respect from mean-minded conformists like you? Let me spell it out. I'm not a martyr because your NRA-style rages are so predictable.

Whine like a mosquito, will you? Fine, just don't bite us again, or you WILL get swatted!

Dale Husband · 24 October 2008

eric said:
Novparl the non-martyr said: I'm not interested in explaining "differential survival" because I don't believe in evolution theology any more than in Christian theology. Evolution, like the resurrection, is a theory, not a fact.
Okay, let me rephrase my question. You say survival of the fittest happens but evolution does not. This piques my curiosity. So I am asking you for more information on your position. If only the strong survive, how does the genome of the species not change? How, for Novparl, does survival of the fittest preserve a genome and keep it from changing over generations?

Perhaps as a Creationist, novparl believes that God made the animals and plants of the world perfect and that there is no need to improve on God's original creation via natural selection. Thus it only keeps the living things of the world in their original state in nature, the way God made them. This is bull$#it, for in nature there is no "perfection", there is only change, and what is ideal for one environment may be unsuitable for another. If the environment changes, then all the animals must do so as well, or go extinct. The only way novparl's assumptions could be valid is if the environments of the world never changed. But they did, as the fossil record, made mostly of strong but extinct animals, proves. The dinosaurs died out and the mammals survived not because the dinosaurs were weaker than the mammals, but because there was a sudden change in the environment that the mammals could adapt to and the dinosaurs could not. Strength or "fitness" had nothing to do with it.

Mrs. · 28 September 2009

Ah but you all are missing the point.

A woman who has c-sections is more limited in her number of offspring because the doctors say so. Less favorable experiences with birth could mean less children. Then women who could have more children with less trauma would be more likely to desire more children. Whether you believe in evolution or what not the large hips small head genes are going to continually get mixed back into the main population. Even if you don't use a gene its still there.
And in the theory of evolution you only change if you have an advantage in changing. With modern medicine we keep many people from dying who should have. We're not evolving this way, we're devolving.

Chelsea · 28 September 2009

C-sections also triple the infant death rate.
http://www.associatedcontent.com/article/1980192/cdc_says_cesarean_triples_neonatal.html?cat=25