Lactose tolerance a key to evolution?

Evidence that we are still evolving, more fuel for the fire…

7http://www.bbc.co.uk/news/science-environment-12535647

At this point in time no more fuel is needed really.

Anyone who denies evolution is denying observable reality and is delusional. More fuel is highly unlikely to change a delusional mind.

But cool link nonetheless :smiley:

Very true, such is the nature of faith. But at least it’s something tangible they could marginally relate to that doesn’t involve God burying dinosuars or them thinking we used to be monkeys ;D

i wonder towards what we are evolving.
since we do less work, our limbs with atrophy, fingers might become longer. even more hairless. or, evolution might be negated completely by us going nano or having bodies cloned and our ‘consciousness’ uploaded to the new brain.

Well, we’re buggering up the ozone layer and putting a lot of dust into the atmosphere, so we’ll need bigger and darker eyes. We aren’t doing as much physical labour, so we’ll get skinnier and nerdier. Most of our communication will be done via touch screens and the like, so our fingers will get longer and fewer. After a while we’ll end up looking like this:


Not anymore.

Lactose tolerance playing a part in human evolution over the last 10 000 years makes a lot of sense. Milk is very nutritious and the role it can play in natural selection is clear. I am less convinced by the story of shorter, fatter people opting to have more children. Have humans not been getting taller? The theory is based on a rather small sample of humanity and also seems to be limited to female parents only.

That is much more the result of improved nutrition than of evolution. Increased height doesn’t confer anywhere near the immediate survival advantage that an ability to metabolise lactose does in an agricultural setting. Also, lactose tolerance is binary (either you can digest it or you can’t), whereas increased average height would be the cumulative effect over successive generations of slight advantages.

'Luthon64

But apparantly kid’s thumbs are getting bigger…

http://news.bbc.co.uk/cbbcnews/hi/sci_tech/newsid_1892000/1892881.stm

Also I think the lack of physical labour is making us fatter and maybe the machines rather make us less intelligent rather than nerdier, so maybe a slightly dumber, fatter alien phenotype.

Hey, remember this song?
PUSA- Man (Opposable Thumb) Cover

Perhaps I misunderstand you, but you appear to juxtapose improved nutrition and evolution as two independent causes. If improved nutrition had no selective effect, it would only impact on the incumbent generation and not have any heritable permanency. There is a cumulative aspect to humans getting taller. Perhaps one should interpret it as indicative of improved nutrition causing both contemporary increased tallness as well as selective advantage. Is that what you intended to convey, but that the former is predominant?

No. Tallness is not genetically fixed in the same way that lactose tolerance is. In any generation, a biological individual may have a genetic predisposition to be taller than its siblings which may endow it with some or other survival (or reproductive) advantage, but that doesn’t mean that the individual will actually attain the potential tallness if the environment isn’t right. The case of the Japanese (and now the Chinese, too) illustrates the point: current generations are taller than their progenitors because their nutritional standards are much improved, not because there’s been a spurt of tallness mutations. That’s the point.

You could of course argue — and correctly so — that the ability to make provision for a healthier diet is itself a product of evolution, and, yes, this ability does indeed provide a selective advantage. Tallness itself is merely a byproduct of that advantage, not the driving trait.

'Luthon64

The exact tallness an individual attains is of course the product of both genetics and nutrition, but I am of the opinion that an evolutionary trend towards increased tallness can be discerned, if not in exactly the same way as the trend towards lactose tolerance, at least in a very similar way. Your modern European is substantially taller than what (say) your Roman soldier used to be two millennia ago. Reverting to the diet of that era would not result in Europeans, within one or a few generations, “shrinking” to that size again. The selection driver is more obvious in the case of lactose tolerance, but tallness has genetically evolved and appears to continue doing so.

when do i get to evolve boneclaws?
(does anybody know a place that deals with adamantium?)

Good point. I suspect the observed increase in (potential maximum) height is at least partly due to sexual selection.

Mintaka

Yes, it would, and within a single generation, too, provided the diet (and lifestyle) reversion is complete and comprehensive in the society under scrutiny. You don’t even need to go back to Roman times. Just 500 years is enough to make the point. As mentioned before, the reverse effect was strikingly illustrated by the Japanese in particular, pretty much over a single generation, where post-war Japanese grew much taller, having been raised during and after the reconstruction years when Japan moved from being an agrarian feudal society to a modern industrial giant. Even today, primitive hunter-gatherer peoples tend to be appreciably shorter than modern societies. For tallness to be a direct evolutionary effect (i.e. directly attributable to genes) there must be a selective advantage, survival and/or reproductive, to being tall that will push the population mean tallness to increasing values over successive generations. While there may indeed be a lesser element of sexual selection to this in modern humans, it’s hardly obvious what that advantage might be, and a significant genetic shift in such a species trait over just a few tens of generations will only be achieved if there is also a commensurately severe selection pressure that drives it. Tallness simply doesn’t fit that profile.

'Luthon64

Each person must be born with the potentiality for both minimum and maximum height. He will reach the latter only under perfect dietary conditions, and the former only under dietary conditions that barely keep him alive.

Reverting to the diet of that era would not result in Europeans, within one or a few generations, "shrinking" to that size again.
Yes, it would,

So the claim is that the minimum potential height of humans remained constant in the last few thousand years, correct?

Mintaka

No, the claim is that the explanation for the observed increase in average human height is not primarily evolution. As said, the combination of slight selective pressure together with the few tens of generations available for genetic fixing is not sufficient to explain adequately the observed increase. It is much more plausibly explained by improvements in people’s living conditions. Japan apart, in Europe, the last 150 years (about six generations) saw an average increase in people’s height of around 14 cm, or ±8%, which is a sizeable change. Moreover, even in relatively homogeneous modern societies, tallness is correlated with socioeconomic status such that wealthier people also tend to be taller, and this difference was much more pronounced just a century ago. That just ain’t evolution. You can read more about the subject here and here.

'Luthon64

Yes, the taller person may indeed be higher up in the pecking order. This contradicts the Framingham study cited by beLIEf in the OP:

"What we have found with height and weight basically is that natural selection appears to be operating to reduce the height and to slightly increase their weight."

We are in agreement that the selection driver is more obvious in the case of lactose tolerance, but a sexual preference for taller people cannot be excluded as a possible influence. The main point I originally made was that claims in the Farmingham study that shorter and fatter people have more children and that that is prove of evolution at work is rather suspect. This would be even more so if evolution played no role in changing tallness.