Last year, Phoenix’s scorching hot summer stretched into the fall. We went nearly four months straight without seeing high temperatures even dip into the double digits.
So, this summer, we’re taking a deeper look at something that can help us mitigate that torturous heat: Shade. From planting trees to building structures, we're asking how we can live more comfortably in these intense conditions. We’re calling this series "Throwing Shade."
Let’s turn to our largest organ: Our skin. From sunscreen to hats to a multimillion-dollar skincare industry to shade, we go to extreme lengths to keep our skin safe from the sun. But, it hasn’t always been that way.
Nina Jablonski, an anthropologist and paleobiologist known for her research into the evolution of skin color in humans, joined The Show to talk about about the history of skin and the sun.
Full conversation
LAUREN GILGER: Begin for us with some of that ancient history, for lack of a better phrase, right? Like, what did the skin of our ancient ancestors likely look like? Like we can study skeleton bones, fossils, things like that, but you know, we don't have prehistoric skin that you can study, right? What do we think it looked like?
NINA JABLONSKI: Exactly. Well, a lot depends on where we start. But if we think about the common ancestor of chimpanzees and humans who lived about 7 or 8 million years ago, they would have looked, probably quite chimpanzee-like in their skin.
But that situation changed a lot, beginning around 2 million or 1.5 million years ago. When we see really modern looking people emerging in Africa, around 1.5 million years ago, what we see is a few really important things.
Loss of most of the body hair that had covered our bodies, and the evolution of dark permanent pigmentation in our skin that protects us from ultraviolet radiation. So, this was super important for protecting us from the bright sun, which was part of our environment.
GILGER: Right. Like people were living in the outdoors all the time and, and human skin used to stand up to it, it sounds in a very different way than it does now. Like these ancient folks were not getting sunburns?
JABLONSKI: I think what we have to recognize is that our ancestors basically lived outdoors. They certainly took shelter when they could, under trees and under rock shelters and so forth, but they were exposed to the elements. And so, the skin was their primary interface between their interior bodies and the outside world. So, the skin did evolve to be incredibly versatile and protective. We think of our skin as being relatively delicate, but actually, it's super tough.
GILGER: That's a really interesting way to look at it, yeah. And we think of it as delicate because we do so much to protect it, right? Like we wear sunscreen, we wear hats. We are very conscious today of skin cancer and protecting our skin and staying out of the sun. We have, you know, protective clothing and shelter and shade and all of these things, but that wasn't always the case.
Tell us a little bit about how that started to change. When did our skin start to adapt because of the way our societies adapted?
JABLONSKI: Well, actually, it's relatively recently, in evolutionary terms. When you think about our species, Homo sapiens, we've been around for over 300,000 years. Our skin really was taking the brunt of the environmental burden until around 25,000 years ago, when we see good evidence for sewn clothing in the archaeological record and evidence for the, you know, dwellings.
And, we especially started covering up and doing these things when we were moving into extreme environments, especially extremely wet and extremely cold environments. When some of our ancestors were moving out of equatorial latitudes, far into Northern Eurasia, for instance, that's when we really get to see a lot of changes in the skin that are related to changes in our position on the Earth's surface.
GILGER: Right. So, this is when I think your research gets really interesting, right? Because you're, you're essentially talking about the development of race and like the different ways in which different skin in different places, pigments. Talk a little bit about how that turned into kind of a way of stratifying societies.
JABLONSKI: It turns out to be a story not so much about race, but about where you live. Because people who were dispersing into northern latitudes, into Eastern Asia and Western Europe, actually underwent independent loss of their dark pigmentation.
So, it doesn't really put them into the same race or different races, it just makes them very different because they have achieved the same appearance or roughly the same appearance, but entirely through entirely independent genetic means.
So, this is really cool because it means that the natural selection pressures in evolution were sufficiently great that these changes had to occur for these people to continue to live successfully in these habitats. And what it means is that, putting people into groups according to their superficial appearance doesn't work at all, because we have a lot of lightly colored people around the world who don't fit into any of the same races.
And similarly, we have a lot of darkly pigmented and highly tannable people who don't fit into the same race. So it's a great evolutionary story, but it's a tragic story with respect to human classification and what we've done with this information on skin color.
GILGER: Yeah, yeah. So let me ask you a kind of forward-looking question to end with, Nina. I mean, as we're watching our environment change right now, right? Like we're watching climate change happen, we're watching, especially here in the Southwest summers become longer, extreme temperatures, extreme exposure to sun really becoming more of the norm.
Having studied the way that the sun has kind of interacted with our skin over the last, you know, many millennia, what are your predictions for how this might change in the future?
JABLONSKI: We will continue to mostly shelter ourselves from the sun. So, in Arizona and other very sunny places, people spend a lot of time indoors, and people who normally spend time indoors, like the vast majority of people do in the summertime, get very good at protecting themselves when they go out of doors because the penalty for not doing that is so great. And the extremes of long summer heat are only going to continue to be more felt over the coming decade.
