Tag Archives: Homo erectus

Hello, Dali

dali

250 thousand years ago

This skull, from China, isn’t much like Homo neanderthalensis or modern Homo sapiens. Both Neanderthals and H. sapiens are specialized in different directions, in ways that aren’t just an automatic consequence of increasing brain size. In Neanderthals, the middle of the face is pulled way forward, in front of a football shaped braincase. In H. sapiens (us), the face is tucked well under the skull, beneath a globular braincase. (We’ll have more to say about these changes later: sapiens skull shape probably has to do with re-engineering the vocal tract.) The Dali skull by contrast looks like a generic transitional late Homo erectus / archaic Homo sapiens (the latter being just a wastebasket, “I dunno. Whaddayou think it is?” category). Most likely Dali is part of/ancestral to an East/Southeast Asian group called Denisovans. Denisovans have come to be known by their genes, which have been found in an ancient Siberian fingerbone, and (at low levels) in some modern Melanesians and Australian aborigines. But we don’t yet know for certain is whether Dali (and similar finds like the less securely dated Jinniushang skull) had these Denisovan genes.

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Heidelberg and Bodo

By 600 thousand years ago we’re finding people who don’t fit comfortably into Homo erectus. A jawbone from around this time was unearthed in Germany, near Heidelberg, in 1907. Another find from the same period, often assigned to the same species, comes from Bodo, Ethiopia (below).

bodo

This guy clearly isn’t modern Homo sapiens, but his brain is starting to get out of the Homo erectus range (1200 cubic centimeters cranial capacity), and his browridge is a double arch, rather than an erectus-style straight bar. He’s also got cut marks on skull and face, from someone “defleshing” him.

The exact relationship of these guys to later humans has been unclear. A popular theory assigned both to an intermediate species, Homo heidelbergensis. However yesterday we reviewed very recent genetic modeling by Rogers and coworkers that suggests that a three-way split between Homo sapiens, Neanderthals, and Denisovans has already happened by this point, although the lineages haven’t had long to differentiate. So probably Heidelbergers in Europe are ancestral to Neanderthals (or at least closely related to their ancestors), while Bodo man is similarly related to Homo sapiens.

Post erectus

629-595 thousand years ago

We’re getting to a time on the blog when Homo erectus (and Homo ergaster, if we accept that erectus-like African specimens are another species) are starting to give way to the very earliest ancestors of later species – Homo sapiens, Neanderthals, and Denisovans. (Denisovans – known mainly from DNA rather than bones – are the contemporaries in East and Southeast Asia  of Neanderthals in West Eurasia, and early sapiens in Africa.) A recent article from Alan Rogers (a colleague of mine in Anthropology at the University of Utah) and Ryan Bohlender and Chad Huff (Utah Anthropology PhDs) sheds light on this period. The authors look at the distribution of shared derived mutations in two modern human genomes (African and Eurasian) and two ancient genomes (Neanderthal and Denisovan). They fit a model involving past divergence times and population sizes to the data. The model says that about 700,000 years ago. a small population split from the rest of humanity and then quickly split again to give rise to the Neanderthals and Denisovans. In other words, it looks like there was an Out Of Africa event in the Middle Pleistocene, well before the better known Out Of Africa event that gave rise to modern human populations around the world. The Neanderthals and Denisovans then replaced Homo erectus in Eurasia, although the authors find signs that some erectus genes may have made it into the Denisovan gene pool.

As paleoanthropologist John Hawks notes, in a commentary on the article, “Humans stand out among our close primate relatives as effective biological invaders. Our recent history has included range expansions into remote and harsh geographic regions, and invasions by some populations into areas long occupied by others.” We’ll be seeing more instances of this in days to come on the blog.

And here’s me on what a history of population replacement might mean for the evolution of ethnicity and ethnocentrism.

Antecessor rising

932-882 thousand years ago

A common way of demeaning another group is to call them cannibals. Roman pagans sometimes accused early Christians of cannibalizing infants during their secret ceremonies (a horror-show misreporting of the Christian Mass?) Later on, medieval Christians sometimes accused Jews of murdering Christian infants and mixing their blood into Passover matzohs. In response to such libels, anthropologists have sometimes swung to the opposite extreme, occasionally even denying that cannibalism (other than emergency survival cannibalism) was ever an established practice. But there is no serious doubt that human populations have sometimes practiced cannibalism, sometimes in the very recent past. In 1961, for example, Michael Rockefeller, traveling in search of tribal art, was killed and eaten by a group on the coast of New Guinea.

At the Grand Dolina site in the Sierra de Atapuerca in northern Spain, the fragmentary remains of 6 people, mostly children, were discovered mixed in with animal bones and stone tools. Animal and human remains were treated the same. In both cases, cut marks show that flesh was cut from the bones. There’s no evidence that the human remains received any specially respectful treatment. Cannibalism is the most plausible explanation.

The researchers involved have proposed a new species name, Homo antecessor, for these and some other early European finds, although not everybody buys this.

Quest for fire

1,043-987 thousand years ago

What really distinguishes humans from other animals? We’ve covered some of the answers already, and will cover more in posts to come. But certainly one of the great human distinctions is that we alone use fire. Fire is recognized as something special not just by scientists, but in the many myths about how humans acquired fire. (It ain’t just Prometheus.) Claude Lévi-Strauss got a whole book out of analyzing South American Indian myths of how the distinction between raw and cooked separates nature from culture. (I admit this is where I get bogged down on Lévi-Strauss.)

Until recently the story about fire was that it came late, toward the latter days of Homo erectus. But Richard Wrangham, a primatologist at Harvard, turned this around with his book Catching Fire (which is not the same as this book), arguing that the taming of fire goes back much earlier, to the origin of Homo erectus. Wrangham argues that it was cooking in particular that set us on the road to humanity. Cooking allows human beings to extract much more of energy from foods (in addition to killing parasites). Homo erectus had smaller teeth and jaw than earlier hominins and probably a smaller gut, and it may have been fire that made this possible. Cooking is also likely to have affected social life, by focusing eating and socializing around a central place. (E O Wilson thinks that home sites favored intense sociality in both social insects and humans.)

Surviving on raw food is difficult for people in a modern high-tech environment and probably impossible for people in traditional settings. Anthropologists are always looking for human universals, and almost always finding exceptions (e.g. the vast majority of societies avoid regular brother-sister marriage, but there are a few exceptions). But cooking seems to be a real, true universal. No society is known where people got by without cooking. Tasmanians, isolated from the rest of the world for 10,000 years, with the simplest technology of any people in recent history, had lost the art of making fire, but still kept fires going and still cooked.

Recent archeological finds have pushed the date for controlled use of fire back to 1 million years ago (see today’s tweet on Wonderwerk cave), but not all the way back to the origin of Homo erectus. This doesn’t mean Wrangham is wrong. Fire sites don’t always preserve very well: we have virtually no archeological evidence of the first Americans controlling fire, but nobody doubts they were doing it. It could be that it will be the geneticists who will settle this one. The Maillard (or browning) reaction that gives cooked meat much of its flavor generates compounds that are toxic to many mammals but not (or not so much) to us. At some point we may learn just how far back genetic adaptations to eating cooked food go.

An alternative to an early date for fire, there is the recent theory that processing food, by chopping it up and mashing it with stone tools, was the crucial early adaptation.

Whenever it is exactly that humans started cooking, the date falls in (Northern hemisphere) grilling season on Logarithmic History, so you can celebrate the taming of fire accordingly. It doesn’t have to be meat you grill. Some anthropologists think cooking veggies was even more important. I recommend sliced eggplant particularly, brushed with olive oil to keep it from sticking, and with salt, pepper, and any other spices.

And here, if it’s your kind of thing, is Iron Maiden doing Quest for Fire.

My handaxe

1.31-1.24 million years ago

By today’s date, Acheulean tools are well developed in Africa, and found in India too. Sophisticated tools like the Acheulean hand axe probably tell us something not just about cognition in relation to tool making, but also about social cognition. You wouldn’t make a hand axe, use it, and abandon it. Nor would you go to all the trouble if the biggest, baddest guy in the group was immediately going to grab it from you. So there is probably some notion of artifacts-as-personal-possessions by the time Acheulean appears.

Possession is a social relationship, a relationship between two or more individuals with respect to the thing possessed. Robinson Crusoe didn’t “own” anything on his island before Friday came along.

Linguists have noted something interesting about the language of possession that maybe tells us something about the psychology of possession: Expressions for possession are often similar to expressions for spatial locations. Compare spatial expressions:

João went to Recife.
Chico stayed in Rio.
The gang kept Zezinho in Salvador.

and corresponding constructions for possessions:

The Crampden estate went to Reginald.
The Hampden estate stayed with Lionel.
Thag kept axe.

Of course the Crampden estate didn’t go anywhere in physical space, but it still traveled in the abstract social space of possession. In some cases just switching from inanimate to animate subject will switch the meaning from locative to possessive. The Russian preposition y means at/near when applied to a place (People are at Nevsky street) but possession when applied to a person (Hat is “at” Ivan = Ivan has hat.)

What may be going on here: people (and many other creatures) have some mental machinery for thinking about physical space. That machinery gets retooled/borrowed/exapted for thinking about more abstract relationships. So the cognitive psychology of space gets retooled for thinking about close and distant social relationships, or time ahead and behind. In other words, we may be seeing a common evolutionary phenomenon of organs evolved for one purpose being put to another purpose – reptile jaw bones evolve into mammalian inner ear bones, dinosaur forelimbs evolve into bird wings. You can find Steve Pinker making this argument in his book The Stuff of Thought. For a while most of the evidence of repurposing spatial cognition for more abstract relationships came from linguistics, but there’s now some corroboration from neurology.

And I’ve made the argument for the particular case of kinship: regularities in kin terminology across cultures tell us something about pan-human ideas of “kinship space.” (My kin and mybody parts are arguably the most basic, intrinsic primitive sorts of possessions, since long before my handaxe.) This implies that the evolutionary psychology of kinship has not just an adaptive component (adaptations for calculating coefficients of relatedness and inbreeding), but also a phylogenetic component  (homologies with the cognitive psychology of space).

We’ll see other possible examples, involving e.g. the evolution of speech sounds, as we move along.

Calories and curves

1.46-1.39 million years ago

energyfat

This figure is from a neat recent paper comparing energy expenditure (TEE or Total Energy Expended) and fat among humans and our closest relations: chimpanzees (genus Pan), gorillas (Gorilla), and orangutans (Pongo). (The numbers are adjusted for differences in overall body mass.)

What stands out here is that humans are a high energy species. Also we carry a lot more body fat than the other great apes. This applies particularly to women, who need a lot of extra fat to meet the high energy demands of human infants. But it even applies to men. For both sexes, a high energy life style means you want to carry around an extra reserve of fat in case of emergencies.

We don’t know how long ago our ancestors decided to crank up their energy consumption. Maybe back with the rise of Homo erectus (just a few days ago on Logarithmic History). Or maybe later, when the typical modern human pattern of slow maturation was more firmly in place. At some point in the near future, we’ll actually nail down the specific genetic changes leading humans to accumulate more fat, and be able to put a date on the change. It may be that the distinctively human mating system also arose back then, with human females concealing ovulation (no chimp-style monthly sexual swellings) but advertising nubility (with conspicuous fat deposits appearing at puberty).

A high energy life-style also goes with extensive food sharing and changes in human kinship. (Here’s me, on beating Hamilton’s rule through socially enforced nepotism.)