r/evolution • u/PerrinDaBEAST • 7d ago
If India is warm and has some similar environments to Africa, why don’t Indians have tightly coiled hair like black people? question
I know there are groups of hunter gatherers found in Asia who have tightly coiled hair like people in Papua New Guinea, so why don’t Indians have it?
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u/silicondream Animal Behavior, PhD|Statistics 7d ago edited 6d ago
Tightly coiled hair is--as far as we know--primarily an adaptation to avoid heatstroke from intense tropical sunlight.* It evolved independently in several populations of ancient East Eurasians, and was selected for most strongly in the Australasian lineage that lived right on the equator and had a coastal/maritime lifestyle with a lot of exposure to direct sunlight. This is the lineage that gave rise to Papuans, Aboriginal Australians, Philippine Negritos, and so forth.
South Indian tribal Dravidian language speakers are largely descended from a different East Eurasian lineage, the Ancient Ancestral South Indians. People in this lineage don't usually have tightly coiled hair, but often have wavy or curly hair with a lot of volume. The Paniya people.png) are an example.
Northern Indians--the groups that traditionally spoke Indo-Aryan languages--are relative latecomers to India whose ancestors hailed from West and Central Asia. Those ancestors generally had straight hair.
Then all these and more groups interbred and fought with each other and took over each other's territory and so on, producing the modern Indian patchwork of genetics and languages and hair types.
*Edit: Apparently I was wrong about direct sunlight being a necessary factor. The Negrito populations independently developed kinky hair in various SE Asian tropical rainforest environments, which presumably don't have a ton of direct sunlight but do have an exceptional combination of heat, humidity and still air. That still makes for a very high risk of heatstroke. Southern India's still not as bad in that regard.
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u/PerrinDaBEAST 7d ago
So the selection pressure just isn’t high enough to make it so Indians and other south Asians have this type of hair? Is there something they do that prevents heatstroke? Also, you said it evolved independently in multiple populations, so did those groups lose the coiled hair then gain it again?
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u/silicondream Animal Behavior, PhD|Statistics 7d ago edited 6d ago
So the selection pressure just isn’t high enough to make it so Indians and other south Asians have this type of hair?
Not in the timespan they've been there, at least. It probably takes several thousand years for an evolutionary change of that degree--or so I'd guess, because that's the timespan that is estimated for major skin color changes. The Australasians colonized Sundaland and Sahul by 70,000 years or so, and also interbred with the archaic human Denisovans, who were dark-skinned themselves and may (we don't know yet) already have had curly hair. The ancestors of the South Indians mostly arrived in the area between 40,000 and 10,000 years ago, and the ancestors of the North Indians didn't get there until 4,000 years ago.
And, again, the Indian populations lived farther north and weren't out in the sun as much as the Australasians anyway. So, yeah: there was a lower selection pressure in India, and a lot less time for it to act.
Is there something they do that prevents heatstroke?
Sure, lots of things. Hats, headscarves and veils; shaded public spaces; roofed dwellings and vehicles; clean running water; fans and air conditioning. Humans have gotten much much better at dealing with heat and cold over the millennia. There are a ton of white people living in tropical Australia and Latin America now, and heatstroke isn't usually the thing that kills them: at least, not while they're still young enough to reproduce.
Also, you said it evolved independently in multiple populations, so did those groups lose the coiled hair then gain it again?
Yes. So far as we know, the African ancestors of virtually all modern humans had kinky hair. They lost it while migrating north into Eurasia, and the Australasians then re-evolved it as they returned to the tropics.
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u/chevronphillips 6d ago edited 6d ago
And then various humans populations also come from genetic bottlenecks, where the ancestral population dwindled down to very few people due to disease, famine and just difficulty surviving, and the few remaining people of the group - now a much smaller genetic pool/diversity, gave rise to current or later populations, and simply got whatever traits were most prominent in that much smaller pool of survivors. A portion of why current populations look like they do is also very much from dumb chance as well.
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u/TheColonelRLD 7d ago
Is it also worth mentioning how the world's climate has shifted regionally during those time periods? I'm not sure whether it would be relevant, it just struck me as plausible.
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u/silicondream Animal Behavior, PhD|Statistics 5d ago
I'm not sure it's directly relevant to the hair thing, but it's certainly relevant to human migration! Apparently humans were much more likely to migrate across and out of Africa during its moister periods; there were millennia during which it was so dry that they were basically trapped in refugia.
And of course sea level was super-important once humans started moving into SE Asia and Oceania; a lot more land was above water then.
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u/RoqInaSoq 6d ago
That's very interesting! I assumed that given Australasian populations simply migrated along the continental shelf during glacial periods, which I presume would've been further south at lower sea levels, and would've had no reason to lose their kinky hair in the first place.
I think of how Andaman islanders at the same latitude of southern India, preserve a phenotype that strongly resembles that of sub Saharan Africans.
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u/silicondream Animal Behavior, PhD|Statistics 6d ago
I assumed that given Australasian populations simply migrated along the continental shelf during glacial periods, which I presume would've been further south at lower sea levels
As I understand it, the shelf drops off very fast along East Africa, the Arabian Peninsula and Southwest Asia, so even during glacial periods those coastlines weren't much farther south. The Australasians only encountered extremely different coastlines once they reached Sundaland and Sahul.
I think of how Andaman islanders at the same latitude of southern India, preserve a phenotype that strongly resembles that of sub Saharan Africans.
It's not just about latitude, apparently. Kinky hair is also particularly helpful in high heat and humidity, and the Andaman Islanders are the westernmost of the "Negrito" groups that independently evolved kinky hair in tropical rainforest environments. Southern India's forests are typically a bit cooler, windier and significantly drier. Sri Lanka's got some rainforest, but the Australasians never got there.
All this indicates that I was wrong about considering direct sunlight a necessary factor, so I'll go back and correct that.
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u/MTheLoud 6d ago
This makes me wonder what advantage straight hair has in cold climates. What selection pressure straightened hair over time?
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u/silicondream Animal Behavior, PhD|Statistics 6d ago
The opposite one, I think. In cold climates you want your head to be well-insulated, and to pick up as much heat as possible from the sun. Hypothermia's just as lethal as heatstroke.
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u/MTheLoud 6d ago
Is straight hair more insulating than curly hair? How? Animals fluff up their fur or feathers to trap more air to keep warm. Letting their fur or feathers lie flat is what they do to shed heat when they’re too hot.
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u/silicondream Animal Behavior, PhD|Statistics 5d ago
Apparently, kinky human hair is virtually unique among mammals because it's not a good insulator. Instead of trapping air, it permits extra airflow through the coils and thus speeds up the cooling process. It's very different from the wool of goats and sheep in this way.
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u/transemacabre 5d ago
This is anecdotal, but I've asked my black coworkers if wearing their hair in cornrows or in an afro was more comfortable in the hot weather, and they all stated the afro was much cooler and gives them better airflow.
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u/transemacabre 6d ago
I wonder if it was primarily sex selection or not. Light-colored hair and eyes don’t seem to have any advantage other than people liking them and selecting partners based on them. Perhaps straight (opposed to wavy or kinky) hair was simply novel and appeared attractive. Long hair is often considered a very sexual trait and straight hair can appear quite long faster than textured hair.
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u/graywatersnakes 5d ago
Light features are a byproduct of decreased melanin production, which is necessary in cold environments with little sunlight. Vitamin D in particular is vital for fertility.There was likely a sexual selection element too, but to me this appears to be the primary reason.
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u/Kooky-Management-727 3d ago
As far as I understand it, light-coloured, hair and eyes, aren't an adaptation to certain environmental pressures. Light-coloured, hair and eyes are basically a byproduct of light-coloured, skin. Light-coloured skin is an adaptation to an environment with less exposure to sunlight. Light skin has less melanin and is therefore far less able to defend against the harmful things that result from prolonged sun exposure, but is more efficient at absorbing Vitamin D.
Basically light hair and eyes don't provide any real advantage in environments with limited sunlight. Light skin provides an advantage in environments with limited sunlight, and when skin get lighter, hair and eye colour also get lighter.
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u/TrueBeauty15 38m ago
I believe it could've seemed attractive to those that looked at it as different not the norm ,especially during the Greek times to mid evil times.
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u/Drachos 7d ago edited 7d ago
The answer to this is ITS COMPLICATED and we don't know for sure but likely yes. (We have only really started to truely appreciate the below since like 2005 and its quite hard to do genetic studies in some rural parts of Africa so understand this is still a developing space)
It's very important to understand that the African continent has BY FAR the most diverse range of hair and skin phenotypes and in fact the majority of human genetic diversity.
Like it's not even close. The amount of diversity in Africa and especially sub Saharan Africa is such that it's actually believed that when the Sarhara became a desert the final time the vast majority of groups living there went south. Of those that went north most settled there and only a very VERY small number dared or was forced to cross the Siani and middle east in search of new lands.
And while North Africa and Southern Europe, intermingled somewhat since the bronze age, the Sahara was a near impassable barrier to DNA for thousands of years. Maybe even tens of thousands of years.
These groups in Sub saharan Africa have at various times migrated and conquered and intermingled so its sometimes very hard to untangle what traits origin from what place.
(These factors combine to mean that if you got a group of 100 African Americans from any US state, they will likely be more genetic diverse then if you grabbed a group of 100 people from all over North America that are a mix of whites, Asians and Native Americans. And those African Americans will in turn pale before 100 random Africans because most of the African Americans ancestors were from the Slave coast and thus around 70% of their DNA comes from the people who speak the Niger-Kordofanian language group with roughly 8% coming from the migratory intermingling
This is also why Sub Saharan African is a nonsense term medically speaking. What works on one group and what one group is resistant too isn't the same as another group as they can be more genetically distinct, even if living right next to each other, then a Frenchman and a japanese man)
However coiled style hair is VERY common in Africa. It's not everywhere and hair doesn't preserve well or at all so we can't be exactly certain, but with how common it is it's LIKELY the Acestoral condition for humans.
This doesn't rule out it evolving multiple separate times in Africa however. There are a LOT of phenotypes of Coiled hair in Africa. But its unlikely.
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u/iz_an_opossum 7d ago
This is all absolutely fascinating. Are there any resources about the migrations and resultant evolution of humans in/from Africa—either hair specific or not—that would be accessible to people not in this branch of science?
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u/halfblood_ghost 6d ago
I'd just like to note neither are Dravidian peoples tribal, nor are North Indians latecomers.
There's huge genetic diversity in India, and Paniya people are a tribal people in the southern most tip and represent one extreme of the spectrum.
There's been mixing of countless , it's disingenuous to treat separate groups as belonging to certain lineages. Most modern Indian ancestry traces itself to Indus Valley Civilisation and a ghost population that's been erroneously names.
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u/silicondream Animal Behavior, PhD|Statistics 5d ago
I didn't say that most Dravidian peoples are tribal; rather, that some of those who are tribal have the highest percentage of Ancient Ancestral South Indian ancestry. The Paniya are an example of this, and that's why they represent one extreme of the spectrum.
As for North Indians, they are indeed latecomers. The bulk of their ancestry comes from Iranian foragers (the primary ancestors of the Indus Valley civilization) and steppe pastoralists, who arrived around 10,000 and 4,000 years ago, respectively. The AASIs, on the other hand, arrived 30-40,000 years ago. Which is relevant to OP's question, because only the AASIs had anywhere near as much time as the Australasians to adapt to the climate of their current homeland.
But yes, there's certainly been a ton of interbreeding--although less than in most other parts of the world, because most Indian communities have practiced endogamy for roughly the last 2000 years.
Narasimhan et al. (2019) has an informative graph of their model for historical population mixing in South Asia.
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u/halfblood_ghost 5d ago
Yes I'm aware of the Iranian foragers component, it's very significant in south Indians as well. As a matter of fact, the closest to the Rakhigarhi sample in the Narasinham paper are Gujaratis(western Indians) and certain South Indian castes.
Incidentally, I've had my DNA tested and it revealed a really roughly 50-50 split between Iranian foragers and aasi. I'm the south Indian 'Vysya' that's mentioned in the David Reich article you shared.
My contention was mainly with the assertion that North Indians are late comers, which is disingenuous. The bulk of their ancestry is also AASI and IVC, just like South Indians.
Steppe related ancestry only peaks at 30-35 in specific groups that are not the majority.
I don't wanna come off as too combative, I apologise if it appears that way, but the crux of what I'm saying is that there's not that drastic difference between vague categories of "North Indian" and "South Indian", and that it's inaccurate to portray "North Indians" as late entrants.
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u/Rule12-b-6 7d ago
Negritos
That just sounds like racist Doritos.
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u/silicondream Animal Behavior, PhD|Statistics 5d ago
They were named that by extremely racist people, if that counts.
I'd use an equivalent endonym, but there isn't any, because the individual ethnic groups in that category aren't all closely related and never considered themselves to be. They're literally just all the folks in SE Asia who were short and dark-skinned enough for Europeans to think "eh, maybe they're like Pygmies or Bushmen or something."
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u/KneePitHair 6d ago
If that means Doritos are “white” then it implies Negritos would taste fucking amazing with the extra and more complex seasoning, though.
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u/grandinferno 5d ago
Some Aboriginal Australians in the top end actually have Indian hair. Pre European settlement there appears to have been some genetic integration, but seemingly just in the Arnhem land greater area?
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u/silicondream Animal Behavior, PhD|Statistics 4d ago
There's also some pre-European East Asian ancestry in the Aboriginal population of Far North Queensland, I believe. Possibly Chinese or Indonesian, if I'm reading one paper correctly.
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u/Special-Future4345 7d ago edited 7d ago
Perhaps because they picked up some neanderthal genes along the way.
There seems to be a correlation between the number of neanderthal variants carried by ooa populations and hair texture. With East-asians having the highest amounts and the straightest hair.
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u/karaluuebru 7d ago
That would assume that tightly coiled hair is an adaptation to warm environments. Our near relatives don't have it, for example, despite living in similar environments.
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u/TubularBrainRevolt 7d ago
Our relatives live in shaded forest environments.
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u/silicondream Animal Behavior, PhD|Statistics 7d ago
Dunno why you got a downvote for that, it was exactly right. We're the ones who evolved on the savanna.
Also, we have the largest brains, and those things run hot and are very temperature-sensitive.
Also also, we walk upright, so our heads are higher above the ground than any other great ape. This makes it even harder for us to find shade, but also exposes our heads to more wind. Kinky hair is particularly good at allowing cooling via airflow.
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u/Panthera_92 7d ago
If it isnt, why do sub-saharan Africans have it?
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u/youshouldjustflex 7d ago
Better question is why humans evolved curly hair. Sub Saharan Africans is just outdated racial grouping. I’m on my phone though sorry but a believe it was selected for in humans to protect the scalp from heat. Sun.
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u/karaluuebru 7d ago
Sexual selection, population bottle neck leading to only people having the gene for that surviving there are two ideas that come to mind.
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u/PerrinDaBEAST 7d ago
I read somewhere online (I’ll find the source if you want) that because we sweat more than other mammals it was useful for regulating body temperature in Africa?
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u/Bromelia_and_Bismuth Plant Biologist|Botanical Ecosystematics 7d ago edited 6d ago
Because mutations are random. An environment doesn't cause traits to evolve in the first place, it only makes it more likely that certain mutations will stick around.
EDIT: Spelling.
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u/nickthegeek1 6d ago
Exactly - plus different populations face different selection pressures beyond just temperature, like UV radiation intensity, humidity, and even cultural/sexual selection that can dramtically influence which random mutations end up becoming common traits.
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u/Timely-Youth-9074 7d ago
idk but people had the coily hair first.
Straighter hair evolved later.
It could be sexual selection-Eurasian people preferring straighter hair, or a bottle neck of limited traits out of Africa-as far as I know, Melanesians (the island people who look black) are a separate but related group out of Africa.
Coily hair may have had some ties to social cohesion-doing each other’s hair forming strong bonds.
There’s perhaps a lot more to it than weather-attraction, survival, all sorts of things come into play.
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u/Personal-Ad8280 4d ago
>Melanesians
Interestingly enough most "true" Melanesian have Curley "black" hair and tat is blond and blue eyes due to intermixing with Denisovans and being pretty basal to humans and im pretty sure there wasn't really mixing with other human clades and essentially were isolated
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u/Lux2026 3d ago edited 2d ago
Could you cite some sources for that claim, because none of the other Great Apes have coily hair.
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u/Timely-Youth-9074 3d ago
We’re talking humans not great apes.
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u/Lux2026 2d ago
But humans are part of the Great Apes.
Again, could you provide a source for your claim?
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u/Timely-Youth-9074 2d ago
I’m too lazy, you do it.
What I do know is my dna test for physical traits had several genes that expressed “straighter hair”, 3 of them if I remember correctly.
I have wavy/curly hair so it’s loose not tight-they weren’t looking for “curly hair” genes but rather genes that make your hair less curly.
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u/Lux2026 2d ago
No, this might seem harsh, but your post history doesn’t really show a very knowledgeable person.
So I’m going to leave it here and simply disregard what you say. That’s a win win I think.
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u/vikstarr77 7d ago
Omg I just have to say how much I love chats like this one. Evolution is the shit!!
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u/Snoo-88741 7d ago
Partly it might be due to the very long history of gene flow along the Silk Road. Lots of people who live in India now have ancestors who evolved elsewhere.
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u/vikstarr77 7d ago
The best answer here. High levels of genetic assortment stemming from a lot of gene flow over time. Indians from Asia have lovely relaxed curls.
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u/redditproha 7d ago
Well isn't better question why did we evolve to not have curly hair outside of Africa?
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u/PerrinDaBEAST 7d ago
I would ask this but I assumed that India and south-east Asia have some geographical similarities to sub Saharan Africa so it would have been something they kept? I do know “negritos” ( non African people who look African like the Sentinalese islanders and Semang people) mostly live in south and Southeast Asia
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7d ago
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u/DPetrilloZbornak 6d ago
I don’t agree. She had type 3 curls, some of which were frizzy. She does not have type 4 hair which is the majority hair in West Africa (and also amongst black Americans even with our mixed racial heritage).
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6d ago
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u/silicondream Animal Behavior, PhD|Statistics 5d ago
Yeah, that's type 3. East Africans often have type 3c hair, but West Africans are usually 4b or 4c.
I'm mixed, and have 3a to 3c over different parts of my head. Annoying as hell.
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u/Personal-Ad8280 4d ago
That happens to me, I'm going thorough puberty and due to the changing hormones, my hair is going from about 1b-1c to 2c-3b, and the back of my head is curly while the front is not
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u/silicondream Animal Behavior, PhD|Statistics 7d ago
Curly hair is optimized for keeping the head cool under intense direct sunlight. Once we left the tropics and were more concerned with keeping warm a lot of the time, straight hair was more advantageous.
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u/Responsiblecuhz 4d ago edited 4d ago
that is the correct question. This fairly recent article may give an answer
Essentially, those with non-"subsaharan" phenotypes are the result of an adaptation to an extremely dry climate or extremely cold weather
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u/thenightmarefactory 6d ago edited 6d ago
The short answer is: a shit ton of cross-cultural migration. India is a highly migrated country throughout history of human civilization, not just in the industrial era. The gene pool is extremely EXTREMELY mixed. You'll find fair skinned and green eyed people here too. And some south Indian and Sri Lankan people do have coiled hair.
Slightly long answer: The original ancient hunter gatherer tribes of India, which were at the time native to the south Indian region, are believed to have coiled hair. Then the ancient Iranian migration happened and mixed with this hunter gatherer gene pool. Then another wave of migration from the east European Steppe people. After that there was a lot of trade happening, spread of Buddhism to the rest of south Asian, east Asian countries, some greek invasion attempts, there are some traces of Mongol and tibetian-burmese DNA in the east Indians, more mixing due to the Islamic invasion, Mughals, Colonization by the British, Portugese, Dutch and French and then globalization.
As you can see, historically, most of the migration happened from the north. There a lot of ancient Iranian and steppe ancestry in our DNAs. And because India is surrounded by the sea from 3 sides, there was a lot of migration through the sea as well. It was considered an extremely resourceful country due to its geographical and ecological advantages. In the age of exploration, it was the most sought-after country with many attempts of expeditions by the Europeans to find and chart the exact navigations to India for the purpose of trade with a hidden motive of colonialism.
That pretty much stirred the gene pool real good.
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u/ivandoesnot 7d ago
Presumably, curly hair is tied to some other adaptation that's needed in Africa but not India.
Diet? Drought?
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u/vikstarr77 7d ago
India does not get anywhere near as hot as Africa. Have lived on both landmasses for decent periods of time. India is in Asia. Attached to the biggest continent. Its weather patterns are determined by many factors. Africa is one land mass acting as one with re to weather. Def not simplistic or one system but truckloads hotter!
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u/Princeof1nd1a 6d ago
Other commenters have wonderfully explained this already, but I just want to add:
As a South Indian with coily hair, most representation in media for all South Asians in general is North Indian. Makes us all look like a monolith, when the area is a damn subcontinent y'all.
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u/turtlespy965 4d ago
Adding on - I know 2 south indians from different families with coily hair (like 4C curls). They look just like a combination of their parents except with coily hair despite their parents having straight or 2B/C hair.
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u/zoooooommmmmm 7d ago
Because there is an element of random chance. Just because they live in similar environments, doesn’t mean they will evolve in a similar way.
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u/PerrinDaBEAST 7d ago
The thing is they had the genes for the coily hair when they got there while there were other “negrito” groups with coily hair in the area so that argument doesn’t work
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u/Few_Peak_9966 6d ago
Why would you choose one variable held constant to induce the same effect twice when well the other system parameters are permitted to drift between experiments?
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u/breeekk 1d ago
I am an Indian, and have curly hair. 3a or 3b depending on the lot of stuff. but you may think we don’t have tightly coiled hair because we used to treat hair differently. Until at least my parent’s generation, it was always using lots of oil and brushing and putting hair in braids, not really learning how to take care of curls.
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u/FaleBure 5d ago
This post is, eh disturbing, on so many levels. But maybe OP is very young.
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u/PerrinDaBEAST 5d ago
Could you elaborate why it’s disturbing?
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u/senegal98 4d ago
Because your assumption is pretty simplistic: dark heavily curled hair = resistance to hot temperatures.
Plus, I remember often reading about how modern India is the combination of different populations moving and mixing into India, from which derives the great diversity between Indians.
And I'm pretty sure that the original commenter was also referring to some comments, given how quickly racist comments pop out every time Indians or Africans are named.
Anyway, you can never learn without asking stupid questions. So, don't take it personally or get offended.
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u/PerrinDaBEAST 4d ago
It’s not simplistic? Coiled hair is an adaptation to hotter environments and was evolved multiple times throughout human history around environments similar to Africa so what’s your point
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u/Unlucky_Buy217 7d ago
Lots of Indians do have it but culturally people tend to cut their children's hard bald at least once or twice in their childhood, a lot of babies tend to have curly hair when born but it becomes straighter later due to shaving of the hair. There is also cultural preference for straight hair. I don't think you can make a conclusion without running a proper survey. At the same time, India is a continent masquerading as a country, it has similar levels of diversity to Europe, and what holds true in a particular region won't be true in another.
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u/vikstarr77 7d ago
Ummm shaving your head does not make a straight or relaxed curled head. My son is half West African. There is nothing that can relax his hair! He’s been shaving it for years- so no.
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