Comments on: What the shades of humanity should be

By: meika

meika — Sat, 02 Feb 2008 01:13:15 +0000

4) i know that tasmanians turned away from marine life and forgot how to make hooks or something by the end of their time on the island.

They stoppped eating scalefish about 4000 years ago, it was probably gender political, as they still dive for crayfish, muttonfish (abalone), and other shellfish. Men did not go in the water, were not allowed to, they probably had an islandwide taboo on scale fish and 'forgot' how to make fishhooks after they stopped eating them, but whatever the reason for the loss, such islands do not receive new tech as there is no trade or population movements to replace what is lost ( to repeat, for whatever reasons - death of an elder, religious nuttery, cultural practice).

Gender political? The food was gathered from the sea and fishing always seems to be more like hunting in hunter-gather societies, for some reason men were no longer allowed/wanted to go in the water (it's too bloody cold if you ask me).

Lizards big and small in central Australia are "gathered" and even though they are the other white meat this food source is not categorized as hunted.

I could go on as to why but I won't just yet.

By: razib

razib — Wed, 30 Jan 2008 04:13:07 +0000

Perhaps it could be that the necessary mutations to change their skin color didn't pop up on demand, and the alleles for dark skin were fixed. Also, the founding population was probably rather small, so it could be a bottleneck which just didn't let in any of the recessive genes floating around.

1) as i said above, the genes for light skin aren't recessive. in fact, one of them KITLG is dominant (i don't really believe that this'll hold up, but whateva).

2) right, the small population size means less variation for selection to work with. totally plausible.

3) but loss of function mutations are pretty easy to come by. so the barrier is lower because of that.

4) i know that tasmanians turned away from marine life and forgot how to make hooks or something by the end of their time on the island.

By: Hyperbole

Hyperbole — Wed, 30 Jan 2008 03:54:05 +0000

Has anyone considered that the Tasmanian population was extremely small, perhaps fewer than 5000 individuals by the time europeans arrived, divided into even smaller clans with limited intermarriage? Perhaps it could be that the necessary mutations to change their skin color didn't pop up on demand, and the alleles for dark skin were fixed. Also, the founding population was probably rather small, so it could be a bottleneck which just didn't let in any of the recessive genes floating around.

Finally, what about diet?

I don't really know, these are things to think about.

By: razib

razib — Tue, 29 Jan 2008 17:31:19 +0000

darren

1) this is a projection based on a model generated from a fit of the empirical data. so no, they're not that dark. they should be as dark as africans, but they aren't (it's a relative scale, so no comment on absolute "how dark should someone be at the equator").

2) the natives of the high andes are i think the darkest numerous indigenous people in the new world though. UV + relatively sunny climate.

By: darrenbk

darrenbk — Tue, 29 Jan 2008 12:33:58 +0000

are the indians near the west coast of south america really that dark, or is that a problem with the graphic?

By: David Boxenhorn

David Boxenhorn — Tue, 29 Jan 2008 01:50:20 +0000

many northern europeans can tan facultatively too

Yeah, what about tanning? Why didn't we develop better tanning ability instead of fixed skin color? After all, we do tan to some degree.

Probably because humans didn't move around all that much...

By: John Emerson

John Emerson — Mon, 28 Jan 2008 18:26:18 +0000

Jaakeli, good point. I was just trying to point out that cloud cover is fairly irrelevant, and that temperature is not coordinated with sun exposure.

By: razib

razib — Mon, 28 Jan 2008 17:38:48 +0000

Not sure what you mean. The genes for lots of melanin in Tasmanian Aboriginal populations are rgarded as recessive, but I have no knowledge of studies backing that up.

i doubt they were recessive. most of the studies coming out in the past 5 years in genomics show that skin color genes exhibit additivity (there is some data on locus which shows dominance for light skin, KITLG). tasmanians could have been recessive of course, but i don't know any pedigree studies (seeing as they went extinct before these sorts of researchers were common!). just google 'skin color' on the search box to the right, i've blogged this before a lot.

Maybe not but it could be sunnier than Spain, (particularly on the east coast, the west is very very wet, but humans tend to avoid it even today)which is not too far from Algeria.

look, there's no reason for all this speculation, OK? you can look these things up! "The evolution of human skin coloration," jablonski & chaplin. google it and look at page 11 (you can find a PDF online). tasmania is like the mediterranean on the map. that makes sense from what i know of the rainshadow on much of the island.

What about the claim that skin melanin is a way to cope with certain kinds of parasitism?

i already made the claim. i'll update when i have more data, right now it's a conjecture....

Could it be said that those with a middling skin color (Mediterranean) have a fitness advantage in the globalized world, since they can more comfortably withstand both cold and equatorial climates?

...perhaps, but

1) olive skinned people have problems with vitamin D deficiency up north.

2) many northern europeans can tan facultatively too. i don't know if the olive-skinned advantage is big enough here (i.e., how many extra hours before folate destruction does it give you?).

By: delorean

delorean — Mon, 28 Jan 2008 17:24:01 +0000

Could it be said that those with a middling skin color (Mediterranean) have a fitness advantage in the globalized world, since they can more comfortably withstand both cold and equatorial climates?

By: Caledonian

Caledonian — Mon, 28 Jan 2008 17:07:30 +0000

I don’t recall any of the native Amerindian groups being especially dark, even those that lived in the Equatorial regions or high in the Andes.

What about the claim that skin melanin is a way to cope with certain kinds of parasitism?

By: jaakkeli

jaakkeli — Mon, 28 Jan 2008 16:11:10 +0000

John, there’s much more to it than that. People on highlands will have much less atmosphere on them than northern Europeans (all northern Europeans except Saamis have traditionally lived barely above sea level). Then there’s terrain: people in mountain valleys might actually get less radiation than expected by height. Then there’s vegetation: living in the forest means spending much more time in the shade than you’d do if you lived on the savannah or the tundra and so on.

The most notable deviation from UV expected based on latitude is probably the Tibetan plateau.

By: John Emerson

John Emerson — Mon, 28 Jan 2008 13:50:31 +0000

As I understand, amount of sunshine is almost purely dependent on latitude for these purposes, because UV radiation passes through clouds. Whereas other factors (continental climate) affect temperature.

By: meika

meika — Mon, 28 Jan 2008 13:25:10 +0000

Razib's "i really doubt that tasmania is sunnier than algeria."

Maybe not but it could be sunnier than Spain, (particularly on the east coast, the west is very very wet, but humans tend to avoid it even today)which is not too far from Algeria.

I don't doubt the tropics get more sun. But we have "excellent weather" here generally.

Don't tell anyone though. We have enough tourists as it is.

By: meika

meika — Mon, 28 Jan 2008 13:05:18 +0000

Razib's

"2) the UV warnings, isn't part of this due to the ozone depletion in the antarctic?"

The Ozone Hole is a looonnngggg way south of here. It's just all water, like from Oregon/Spain to the North pole being all water. World maps don't emphasize this much.

"3) the population of northern europeans who settled in australia are very depigmented for the latituded."

Not sure what you mean. The genes for lots of melanin in Tasmanian Aboriginal populations are rgarded as recessive, but I have no knowledge of studies backing that up.

By: bioIgnoramus

bioIgnoramus — Mon, 28 Jan 2008 12:55:52 +0000

The way to stop the boys discussing IQ, Razza, is to get ‘em talking about “hotties”.

By: razib

razib — Mon, 28 Jan 2008 11:29:29 +0000

can we not turn this into a discussion about IQ? pretty soon no one will be talking about anything else….

By: jaspa

jaspa — Mon, 28 Jan 2008 11:12:14 +0000

Er Vantage, are you saying I’m poor as well as dump,or is it the other way around :)

By: razib

razib — Mon, 28 Jan 2008 10:46:11 +0000

Tasmania has lots of sunshine, despite chilly winters they didn't wear a lot of clothes, and I don't know about that satellite data, we have a lot of UV in summer, UV warning on weather forecasts are very common, we are at the same lattitude as northern Spain/ Oregon. The east coast is not very cloudy and in a rain shadow.

I doubt mutations dropping melanin would prosper.

this is an important point, but

1) melanin dropping mutations did prosper at equivalent latitudes in east asia and europe. compare the typical spaniard or algerian to a photo of a tasmanian. i really doubt that tasmania is sunnier than algeria.

2) the UV warnings, isn't part of this due to the ozone depletion in the antarctic?

3) the population of northern europeans who settled in australia are very depigmented for the latituded.

By: razib

razib — Mon, 28 Jan 2008 10:43:58 +0000

toto, the frequency in the punjab is quite a bit higher than the rest of south asia. on average punjabis are still more similar to other south asians than they are to persians, for example, but they have a lot more west eurasian lineages than other south asian groups (the frequency varies by study and how they assign the lineage).

vantage: does this interesting (ahem) study include the notoriously dark-skinned, though historically advanced Tamils?

we've gone over this. the correlation between skin color & IQ can't be connected to a common causal factor. there were 4-5 QTLs of very large effect for skin color trait value, no large known QLTs for IQ.

By: toto

toto — Mon, 28 Jan 2008 10:10:15 +0000

(Mods: please delete my previous posts)

Jaspa: About 40% of mtdna from NW India seems to be of 'recent' Middle Eastern/Med origin

Are you sure? From Kivisild's PhD thesis (2000, p.29): Both East and West Eurasian specific haplogroups in Indians are represented by deep Indian-specific branches. The primary clustering of mtDNA lineages is not language-specific (Hindi, Dravidic) and only a small fraction of Indian mtDNA lineages (less than 10%) can be ascribed to a relatively recent admixture with western Eurasians ... An attempt to date their arrival was made that yielded an estimate of about 9,000 years. This date, however, is most likely an average of a number of different West Eurasian donations to the Indian gene pool.As for the social aspects of skin colour, although there is strong preference for fairer skin throughout South Asia, we should remember that the "palest" South Asian group (the Pashtuns/Pathans) is generally regarded as "low-status" by other local populations (at least that's what I'm getting from one Punjabi source...)

vantage: does this interesting (ahem) study include the notoriously dark-skinned, though historically advanced Tamils?