Curly Hair May Have Been Crucial for Early Humans in Equatorial Africa

[joshwallerr]

Curly hair may have been a crucial adaptation for early humans living in equatorial Africa, as it provided effective protection from the sun’s heat and minimized the need for sweating, according to a new study published in the journal PNAS.

This passive cooling mechanism likely allowed for brain growth by conserving water and reducing heat.

Full story available here: https://newsnotfound.com/study-finds-curly-hair-may-have-been-crucial-for-early-humans-in-equatorial-africa/

[Genady]

There is a gap in logic between finding that scalp hair reduces the amount of heat gain from solar radiation and stating that scalp hair likely evolved as a way to reduce the amount of heat gain from solar radiation. What is the evidence that it was a crucial adaptation? Isn't it one more "just so" story?

[Genady]

1 hour ago, joshwallerr said:

This passive cooling mechanism likely allowed for brain growth by conserving water and reducing heat.

By what mechanism conserving water and reducing heat allowed for brain growth? Why is it likely?

[TheVat]

I looked at the PNAS paper.  It studied the mechanism of curled hairs in thermoregulation but said that the evolutionary aspect was speculative.  Curled hair could have other adaptive value, and the thermoregulation is just a Gouldian spandrel.  (straight hair is prevalent on the Indian subcontinent and SE Asia, a situation which doesn't support the idea that there would be adaptive pressure for curly hair in hot regions)

https://www.pnas.org/doi/10.1073/pnas.2301760120

They concluded

Maximal evaporative heat loss potential from the scalp is reduced by the presence of hair, but the amount of sweat required on the scalp to balance the incoming solar heat (i.e., zero heat gain) is reduced in the presence of hair. Particularly, we find that hair that is more tightly curled offers increased protection against heat gain from solar radiation.

[Genady]

Wouldn't a hair that is more tightly curled offer increased thermal insulation in cold environments? Wouldn't it reduce heat loss from the head in temperate and colder climates? Wouldn't it be advantageous as humans moved out of the Equatorial Africa?

[Phi for All]

!

Moderator Note

Moved to Science News. 

joshwallerr, calling attention to science stories in the news is what our Science News section is for, but ultimately this is a science DISCUSSION forum. If your goal is only to promote your website, you're in violation of our rules. We want to have a conversation about your topics, with you involved in it, otherwise you're just selling something. Thanks for understanding.

 

[mistermack]

11 hours ago, joshwallerr said:

Curly hair may have been a crucial adaptation for early humans living in equatorial Africa

Is there evidence that early humans had curly hair? I wasn't aware of any. 

Head hair on humans is not likely to be retained for function, but for sexual signals. Or possibly as something for infants to cling to (in women). Or both. 

Curly hair might be just a result of a larger diameter of hair. On me, at least, the fine hairs seem straighter than the thicker ones. Maybe thick hairs naturally grow curly.

[CharonY]

16 minutes ago, mistermack said:

Is there evidence that early humans had curly hair? I wasn't aware of any. 

Yes, quite a few. Genetic analyses found that mutations leading to straighter or wavy (ass opposed to curly) hair arose later in outside of Africa. However, even without genetic data, looking at the likeliest scenario of the current dominance of curly hair in Africa, is that it is the original phenotype.