Australopithecus afarensis is one of our most famous relatives. Although you might not recognise the name, you're likely familiar with the most famous member of that species: Lucy. This fossil reveals the species was much more ape-like than us. But don't let that fool you. A new analysis of their "palaeodiet" has revealed the species was very successful.
Hadar, Ethiopia, documents nearly half a million years of Australopithecus existence. Over the course of this period, the climate changed. Whilst many other animals had to adapt to this environmental shift, Lucy's crew didn't. They were able to survive whatever nature threw at them with ease. Even when our family looked like apes, we flourished like humans.
Half a million years of Hadar
The Hadar site is kind of a big deal for several reasons. For starters, it's a very rich site with more than 300 animal fossils. But its biggest claim to fame comes from just one of those: Lucy. She shot to stardom after her discovery in the 70s as the closest to complete member of the early human family. Since then many other fossils have taken that prize (some from Hadar as well), but Lucy still has a special place in the publics' heart.
Although for this research she's fairly irrelevant. In this case, what makes the formation critical isn't it's quantity of fossils. Or the quality of them. Rather, the time period they document is key. The fossils from Hadar were deposited over at least half a million years, from 3.4 million years ago onwards. FYI, Lucy falls in at around 3.2 million years old.
This means that scientists can not only study individuals and species (like Lucy), but how they changed over time. How did these animals (and our ancestors) adapt to changes in climate, changes in food availability, and preferred environments vanishing?
Stable isotope analysis is a great way of investigating diet and climate in the past. The gist of this approach is that you are what you eat. Different food sources (in different environments) contain different isotopes. These are simply variants of elements produced by the differing environmental conditions. As your food is incorporated into your body, the unique isotope fingerprint of it is preserved as well.
So by examining the stable isotope data from hundreds of animals (including Australopithecus afarensis) over the half million years of Hadar, researchers could investigate how diet, climate, and more changed over that time. And, perhaps more interestingly, how those animals adapted to that change.
Lucy's palaeodiet
The stable isotope data from Hadar represents one of the largest collections ever, covering one of the longest periods of time ever studied so systematically. The results are appropriately interesting. All sorts of charts and numbers depicting how bovids (i.e. related to cows) changed their diet over the half a million years.
Of course, we really only care about our own family. And it turns out that Australopithecus afarensis had a fairly unique niche in the Hadar environment. Their diet seems to have been very flexible, covering a broad range of foodstuffs. In fact, they had the most varied diet of any animal examined at Hadar. That said, a varied diet isn't necessarily that unique. Many other animals also practiced this strategy. However, they often had to adapt to their diet overtime; focusing on different parts of their diet depending on availability. Meanwhile, our early relatives don't seem to have made such sacrifices.
Lucy and her crew seem to have had a relatively unique palaeodiet, that was hugely varied but didn't need to change much over time. This would suggest that Australopithecus and their flexible diet was extremely well suited to the Hadar environment, able to easily withstand any environmental change within their existing dietary capacity.
As an aside, some might take issue with claiming Lucy had a palaeodiet. Technically speaking, she does pre-date the palaeolithic. However, that simply refers to the period during which our ancestors made stone tools. And new discoveries push back the invention of stone tools, to around the time of Lucy. So really, her species didn't just have the palaeodiet. They invented the palaeodiet.
At least, they invented the real one. Not the modern fad, which involves eating a lot more domesticated animals than I think were available during the stone age.
Lucy's palaeodiet is the secret to our success
This data shows Australopithecus afarensis had an extremely varied diet. This flexibility helped them succeed in the Hadar environment, able to take any environmental changes in their stride. This sort of flexibility wasn't unique amongst the Hadar animals. Others had a flexible diet. Some even managed to not change that much during the studied time period. If you just looked at all the animals living there today, Lucy and her kin would really stand out to you. Except, perhaps, as having the most varied diet in Hadar.
That accolade might not seem like much, but it likely had huge implications for our evolution. Flexible behaviour is what makes humans successful. When we encounter a problem, we don't evolve around it. We think around it. Some even postulate that this drive to "insulate" ourselves from the environment might have been what helped our brain to evolve so big.
This sort of flexibility is what made our species successful. And Lucy had it too. Her species was taking baby steps, but those small steps add up.
References
Johanson, D.C., Lovejoy, C.O., Kimbel, W.H., White, T.D., Ward, S.C., Bush, M.E., Latimer, B.M. and Coppens, Y., 1982. Morphology of the Pliocene partial hominid skeleton (AL 288‐1) from the Hadar formation, Ethiopia. American Journal of Physical Anthropology, 57(4), pp.403-451.
Wynn, J.G., Reed, K.E., Sponheimer, M., Kimbel, W.H., Alemseged, Z., Bedaso, Z.K. and Campisano, C.J., 2016. Dietary flexibility of Australopithecus afarensis in the face of paleoecological change during the middle Pliocene: Faunal evidence from Hadar, Ethiopia. Journal of Human Evolution, 99, pp.93-106.
