The history of human evolution has become firmly wedded to the Out of Africa hypothesis: the idea that we evolved in Africa and from there spread around the world. Back in 2015, palaeoanthropologist David R. Begun gave the proverbial tree of life a firm shake with The Real Planet of the Apes, making the case that the picture is a bit more complicated than that. Providing an incredibly well-written overview of the deep evolutionary history of great apes and humans, an interesting picture emerges of species moving into and out of Africa over time. Some reviewers hailed it as provocative – but is it really?
In case you are wondering why I am only now reviewing a book published in 2015: I had just started reading the foreword of the recently published Ancient Bones when it occurred to me that its spiel – our deep evolutionary history lies in Europe rather than Africa – sounded familiar, as did the name of its writer, David R. Begun. Where did I read about this before? One glance at my bookshelves confirmed that, yes, Begun wrote The Real Planet of the Apes which I bought some years ago but had not yet read. Better late than never.
With this book, Begun takes the long view, surveying the deep evolutionary past of the ancestors of great apes and humans, i.e. the period from approximately 35 to 7 million years ago (mya). His starting point is the split between the ancestors of New World monkeys (which went off on their own evolutionary experiment in South America), and the ancestors of Old World monkeys and hominoids (humans, lesser and great apes, plus all their ancestors). Begun would some years later contribute a very readable 10-page summary of archaic ape evolution to Gurche’s Lost Anatomies, but the executive summary would be: out of Africa, into Europe, and then back into Africa.
“[…] Begun takes the long view, surveying the deep evolutionary past of the ancestors of great apes and humans”
A bird’s-eye-view version of his argument starts with the great diversity of catarrhine* primates flourishing in Africa from the Oligocene into the early Miocene (~33 to 17 mya), including Aegyptopithecus (a “not-quite-ape”), Kamoyapithecus (“possibly the first ape?”), and the intermediate monkey-ape genera Proconsul and Ekembo. Then, by 17 mya, Afropithecus and the closely related Heliopithecus show up in East Africa and expand their range into Eurasia. While Asia sees its own flourishing of species in what is by now the middle Miocene, Europe is the epicentre of the overall story and sees the evolution of Griphopithecus and Dryopithecus around 15-13 mya. Four descendants of Dryopithecus (Hispanopithecus, Rudapithecus, Ouranopithecus, and Oreopithecus) are discussed here in particular.
Meanwhile, the fossil record in Africa seems to dry up. Are we yet to find crucial fossils from this period? Possibly, but Begun points out we have plenty of other fossil mammals from these areas and the environment back then would have been suitable for apes. There are some questionable African fossils from this period discussed here, but nothing convincing. By ~10 mya, climatic changes forced the Eurasian great apes to reinvade Africa where the first hominins appear by ~7 mya; Sahelantropus tchadensis is mentioned in particular.
Now, in case you think that this makes for a neat linear story, let me stop you there. For the sake of brevity, I have skipped over many side branches and dead ends that Begun discusses here. Evolution resembles a tangle more than a tree. Although his ideas are not accepted by everyone (show me a group of scientists not endlessly arguing finer points), are his ideas really this much at odds with the established Out of Africa story? Let me offer three observations.
“[…] your narrative depends on what period you take as your starting point and what groups you consider, which can make the whole Out of Africa narrative sound a bit arbitrary”
First, definitions matter. Casual use of the phrase “Out of Africa” in the popular press often fails to mention the when. Some researchers use it to talk about Pleistocene migrations into Europe by hominins such as Homo erectus, though it more commonly refers to the spread of anatomically modern humans from Africa between 300,000 to 200,000 years ago. Begun ends his story some 7 mya, which is when many popular accounts start theirs. Although I do not know if Mark Maslin agrees with Begun’s thesis, the scenario laid out in his book The Cradle of Humanity is perfectly congruent with it. Maslin’s starts around 5 mya and Begun agrees that the fossil record situates early hominins in Africa by this time. My thoughts after reading this book are that your narrative depends on what period you take as your starting point and what groups you consider, which can make the whole Out of Africa narrative sound a bit arbitrary. Even Begun’s ideas could be cast as an Out of Africa scenario.
Second, the recent ancient DNA revolution has splendidly revealed how populations have constantly moved and mixed. Though this technology only allows us to look back hundreds of thousands of years, there is no reason to think the pattern differed drastically before that. Especially as pretty much all palaeoanthropologists agree that climatic changes are an important driver of migration: Begun does so here, Maslin does, even the Leakeys – focused as they are on human evolution in Africa – do.
Third, Begun’s claims might be provocative, but his delivery is not. Instead, his account is tempered and reasonable, clearly indicating where and why his ideas diverge. He might not always agree with others but nevertheless goes on record here to praise their track record. The most severe criticism he expresses (and that is putting it strongly) is that he follows a philosophical approach of putting evidence before process (e.g. the Out of Africa hypothesis). In his opinion, others lean towards putting process before evidence, ignoring or downplaying evidence that does not fit. He thinks that most of the research community has mischaracterised the European branch of the ape family during the middle to late Miocene as little more than an exotic sideshow. But he also repeats throughout how he is open to changing his mind with future fossil finds. Basically, I see someone of intellectual integrity here.
“[…] Though [ancient DNA] only allows us to look back hundreds of thousands of years, there is no reason to think [migration patterns] differed drastically before that. Especially as pretty much all palaeoanthropologists agree that climatic changes are an important driver”
And there is much else to like here. Begun clearly, and if necessary repeatedly, clarifies terminology, whether it is cladistics or skeletal morphology. He also offers excellent explanations of how we reconstruct past climates. How the rules around taxonomical nomenclature work. How plate tectonics influenced biogeography, specifically how, as the Tethys Sea was closing up, rising and falling sea levels revealed and sundered land bridges, opening or closing migratory routes in the Mediterranean and Arabian Peninsula. And how, with modern technology (and often a lot of hard work) we can extract unbelievable detail from fossil teeth, which are frequently the only remains we find. Additionally, he spices up his writing with introductions to the typical fauna of the different periods, short excursions into the history of palaeoanthropology as a discipline, and personal anecdotes of old-guard researchers he met or worked with.
Seeing the book’s age, it is relevant to ask what has happened since publication to change or reinforce this idea. When I contacted Begun, he confirmed that there have been no major finds to overthrow his ideas, with new work adding further support. I will next turn to the 12-million-year-old finds recently described in Ancient Bones. Also of interest is the story of the 4.4 million-year-old Ardipithecus, one of the last species Begun mentions, which is told in more detail in the recently published Fossil Men.
I was not all that familiar with the earliest chapters of primate evolution, so, all in all, I found The Real Planet of the Apes an incredibly engaging and useful account.
* Catarrhines are a taxonomical group that encompasses humans, great apes, hylobatids such as gibbons, old-world monkeys, and all their ancestors before these various groups split from one another.
Other recommended books mentioned in this review: