- [Hank] Earlier this week, biotech company Pfizer announced that the vaccine it's developing for COVID-19 is 90% effective. And that is very exciting news. It also comes with some pretty big caveats, including the fact that they haven't formally published peer-reviewed results yet.

We're gonna spend some time working on that story. We don't wanna come to you with something rushed. We wanna think it through, talk it through, figure it out, all the little details here and there, so that's coming next week. Until then, enjoy this news from the world of paleoanthropology. 

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There's a persistent stereotype that our early human ancestors had clear gender roles. Men were hunters, while women were gatherers and foragers. While that's obviously an overly simplistic picture of diverse and complex social structures, research published last week in Science Advances presented evidence that some of the earliest big game hunters were female.

Back in 2013, a local indigenous man found a 9000-year-old burial site about 4000 meters high in the Andes Mountains in Peru. Then, in 2018, a research group visited the site with permission from the local community, where they found multiple sets of human remains, hunting tools including projectile points, and other tools for hunting and processing animals.

Since folks were often buried with their earthly possessions, it was fair to assume that one of the people in the graves was a hunter during their lifetime. The team's bone expert determined that the set of bones was probably female by the looks of their femur, and, back in the lab, an analysis of proteins from the subject's teeth confirmed that it was a female skeleton. This analysis involved amelogenin, a protein in teeth that can come from either the X or Y chromosome and looks slightly different in each case.

Now, a single burial doesn't necessarily mean scientists throw out everything they know about prehistoric division of labor, so the researchers started looking for patterns in other early human burials. They looked through documentation of burials in the Americas from around the same time. They narrowed their results to just skeletons that were buried with similar big game hunting tools and came up with 27 individuals. 16 of them were male, while 11, including the new skeleton, were female.

According to the researchers, this is evidence that women not only participated in the hunting activities but might have accounted for up to half of the hunting population. Their society's diet may have consisted mostly of animal meat, so it would make sense to have all hands on deck to help hunt.

That conclusion comes with some caveats, though. We can say very little about how these ancient people felt about gender and gender roles, since the study mostly only tells us about their physiology. But we can say that the cultural position of these individuals doesn't match up with what we've assumed.

The researchers limited their search to the Americas, so we can't necessarily say that early humans in Asia or Africa had similar social setups. Plus, many present-day cultures, including hunter-gatherers, do seem to fall into this gendered divide where men do most of the hunting.

Since that's the case, though, this study raises some new questions. It tells us we can't project modern understandings of gender roles onto the past. But that means we'd like to know how gendered divisions of labor changed over time and from place to place.

Another recently published article in Nature, Ecology, and Evolution also gives us a better understanding of gender and human bodies, albeit from much, much earlier. Before this study, we thought that males from the extinct human species Paranthropus robustus were much larger than females, a phenomenon called sexual dimorphism. That's because, when previous research looked at fossilized Paranthropus remains found in South Africa, it seemed like the males were noticeably bigger than the females.

These guys lived alongside our ancestors, members of the genus Homo, about two million years ago. This new research describes a Paranthropus specimen that's about 200,000 years older. But here's the thing. A newly found, nearly complete skull was identified as male and was much smaller than expected. That made the researchers think that the size difference wasn't sexual dimorphism but just differences between the two samples of fossils.

With that in mind, the researchers had a new question to tackle. If Paranthropus used to smaller, how and why did they get bigger over time? Well, around the time Paranthropus and Homo showed up, another early human relative, Australopithecus, was on its way out, and the climate in the region got much cooler and drier, which led to rapid evolutionary change as these early humans adjusted to eating much tougher plants.

The idea is that Paranthropus and Homo adjusted way better than Australopithecus did, and part of that adjustment may have had to do with how Paranthropus chewed their food. The newly found, much older specimen had a less powerful jaw and chewing muscles, which could mean that they evolved a stronger bite force and bigger teeth to process those tough plants better.

And that made the researchers think the overall size difference could have been another one of these evolutionary adjustments. The researchers used these findings to caution others in their field about making assumptions based on a limited fossil record. Knowing what kind of evolutionary pressure early humans faced gives us a more complete picture of how modern bodies came to be a thing. And, of course, it reminds us to keep our assumptions about sex and gender in check.

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