evolution likes it hot

i posted about this before, but the topic came up in conversation recently, so i thought i’d post about it again:

“Evolution faster when it’s warmer”
24 June 2009

“Climate could have a direct effect on the speed of ‘molecular evolution’ in mammals, according to a study.

“Researchers have found that, among pairs of mammals of the same species, the DNA of those living in warmer climates changes at a faster rate.

“These mutations – where one letter of the DNA code is substituted for another – are a first step in evolution.

“The study, reported in Proceedings of the Royal Society B, could help explain why the tropics are so species-rich….

“The idea that microevolution happens faster in warmer environments is not new. But this is the first time the effect has been shown in mammals, which regulate their own body temperature.

“‘The result was unexpected,’ said Len Gillman from Auckland University of Technology, who led the study.

“‘We have previously found a similar result for plant species and other groups have seen it in marine animals. But since these are “ectotherms” – their body temperature is controlled directly by the environment – everyone assumed that the effect was caused by climate altering their metabolic rate….’

“‘We suspected the same effect might be happening in mammals, because seasonal changes affect the animals’ activity,’ Dr Gillman told BBC News.

“He and his team compared the DNA of 130 pairs of mammals, looking at genetically similar ‘sister species’ – where each of the pair lived at a different latitude or elevation.

“They tracked changes in one gene that codes for a protein known as cytochrome b, comparing the same gene in each of the pair of mammals to a “reference” gene in a common ancestor.

“By looking for mutations in the DNA code for this gene – each point where one letter in the code was substituted for another – the researchers were able to see which of the two mammals had ‘microevolved’ faster.

“Animals living in environments where the climate was warmer, had about 1.5 times more of these substitutions than the animals living in cooler environments.

“Dr Gillman explained that, at higher latitudes where environments are colder and less productive, animals often conserve their energy – hibernating or resting to reduce their metabolic activity.

“‘In warmer climates annual metabolic activity is likely to be greater, so this will lead to more total cell divisions per year in the germline.’

“These results support the idea that high tropical biodiversity is caused by faster rates of evolution in warmer climates.”
_____

here’s the original research article: Latitude, elevation and the tempo of molecular evolution in mammals

one of the first things that popped into my mind — right after cool! — when hearing about this a few years ago was: so what could this mean for the out-of-africa (ooa) theory? one of the foundational pillars of ooa is that, because genetic variation is greatest in africans, they must be some of the oldest populations on earth ’cause they’ve acquired so many, many mutations — therefore, everyone else prolly came ooa:

“A 10-year study published in 2009 analyzed the patterns of variation at 1,327 DNA markers of 121 African populations, 4 African American populations, and 60 non-African populations. The research showed that there is more human genetic diversity in Africa than anywhere else on Earth….

“Human genetic diversity decreases in native populations with migratory distance from Africa and this is thought to be the result of bottlenecks during human migration, which are events that temporarily reduce population size. It has been shown that variations in skull measurements decrease with distance from Africa at the same rate as the decrease in genetic diversity. These data support the Out of Africa theory over the multiregional origin of modern humans hypothesis.”

but if genetic variation might be increased just by living in a hot climate … well … then what?

more recently, davidski over at eurogenes posted about this paper the other day: An Abundance of Rare Functional Variants in 202 Drug Target Genes Sequenced in 14,002 People. turns out african americans have a lot more rare genetic variants than europeans — and northern europeans have the least of all:

could the differences be related to the fact that these people’s ancestors came from different latitudes/climates and, so, their mutation rates were different? dunno. maybe.

previously: here’s my question

(note: comments do not require an email. chillin’.)

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8 Comments

  1. It’s not body temperature that controls the rate of evolution, it is the availability and abundance of resources. The rich resource base of the tropics provides ample opportunity for new mutations to become established. I’m surprised the scientists are too ignorant to know this. But then, the really good scientists go into physics, math and chemistry.

    If AGW is correct, the main effect would be to warm the temperate and polar regions.
    The tropics would change only slightly. This might reduce the differential in evolutionary rates.

    Reply

  2. @bob – “It’s not body temperature that controls the rate of evolution, it is the availability and abundance of resources.”

    seems to be the heat for plants — increases their metabolic rate. maybe/possibly. of course, the same mechanism (if that’s what’s happening in plants) doesn’t have to apply to animals.

    whatever the cause, it looks like there are more mutations in warmer climes — more for good ol’ natural selection to act upon.

    Reply

  3. hbd chick, these two vids explain human genetic diversity and why Africa is the cradle of mankind. I thought they were straightforward:

    Reply

  4. @insightful – “these two vids explain human genetic diversity and why Africa is the cradle of mankind.”

    very nice videos, insightful, thanks. but they (and, i guess, you) miss the point of my post. the videos say something to the effect of how we can trace the migrations of humans out of africa because we know the rate of mutations. but if that rate is faster in hotter climates than in cooler ones … (think about that for a sec) … mightn’t that mean that the greater genetic variety in african populations could simply have something to do the fact that most of the continent lies in the tropics?

    Reply

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