Ardi

4.4 Mya

We’ve got earlier hominins – Sahelanthropus, Orrorin tugensis, even an earlier species of Ardipithecus – but Ardi (her nickname, her species is Ardipithecus ramidus) stands out because she left us an exceptionally complete skeleton. 

And she helped to upend a lot of theories based on drawing a straight line between modern chimpanzees and later australopithecines. She was a biped. Her legs tucked under her pelvis, with a short lower spine, and a broad pelvis (all closer to modern humans than to chimps). Her outer foot was adapted for walking on the ground. But her toes were long-ish. And her big toe stood way off to the side: well-adapted for grasping branches. So when she was walking on the ground, she had to use her second toe to push off, instead of – like you and me – her big toe.

Ardi really shifted people to realizing that gorillas and chimps are specialized beasts, specialized in being big apes adept at climbing trees, grasping branches, swinging around, and pulling themselves up by their arms, but paying a price in inefficient knuckle walking when down on the ground. Ardi was taking up a different specialization, still a tree climber (her habitat was woodland, more than savannah), but ambling around (not quite striding yet) two-legged on the ground. 

So the common ancestor of chimps and humans, back before Ardi, apparently didn’t look all that much like either. In some respects she might have been somewhat closer to humans. She might even have been a sometime biped on the ground.

For a great recent summary, including lots of information about Ardi, and also about the politics, academic and otherwise, of digging fossils, check out Fossil Men: The Quest for the Oldest Skeleton and the Origins of Humankind.

Toumaï

7.04 – 6.67 million years ago

Sahelanthropus is a 7-6 million year old species whose remains have been found in Chad. “Toumaï” (“hope of life” in the Daza language) is the nickname for one individual, represented by a fairly complete skull. Otherwise Sahelanthropus is known from some jaws and teeth.

One of the things that distinguishes hominins (the human line) from great apes is that the front teeth – canines and incisors – are reduced. (Back teeth are another story. They stay big, or even get bigger, for a long time.) By this standard, Sahelanthropus looks like an early hominin. It’s got reduced incisors and canines and a short mid-face. And depending on who you talk to, it might or might not have been bipedal, although the foramen magnum (where the spine enters the skull) was maybe not positioned to balance the skull on top of the spine. Not that there was much brain inside the skull: the cranial capacity (maybe 360 cc) would be at the low end for a chimp.

So Sahelanthropus could be one of the very first species related to us after the chimp/human split. Chad, where Sahelanthropus was found, is a long way from East Africa, where most other hominins have been found, which suggests there may have been a profusion of hominins across Africa, waiting to be discovered.

The face in the Logarithmic History banner for the month of May is a Sahelanthropus.

Tutsi and Hutu

In just one hundred days in 1994, some 800,000 Rwandan Tutsi were murdered under the direction of the Rwandan government, with the participation of a large part of Rwanda’s Hutu majority population. This was genocide, the last major genocide of the twentieth century. However US diplomats were forbidden to use the word. Calling it genocide would have obliged the international community to intervene.

A few comments:

The internal violence in Rwanda was closely linked to external conflict. Next door to Rwanda is Burundi, with a similar demography – a Tutsi minority and a Hutu majority. But politics took a different course in the two countries. In Rwanda the Hutu took power when the country attained its independence in 1963, and the government directed massacres of Tutsi. Meanwhile, in independent Burundi, the Tutsi dominated, In 1972 100,000 Hutu were massacred there, while the next year saw anti-Tutsi riots in Rwanda. The genocide in 1994 followed a seizure of power by Hutu extremists, who played on fears of a Tutsi takeover. French political scientist Jacques Semelin calls Rwanda and Burundi “ethnic false twins.” He notes similar “fratricidal duos” in the case of other twentieth century genocides – Serbia and Croatia, Nazi Germany and the Soviet Union, Ottoman Turkey and Czarist Russia. In each case, mass killing of ethnic minorities – of Croats, Jews, Armenians –  was tied, in the minds of the perpetrators at least, to life-and-death external threats.

The history of the Tutsi and the Hutu goes back a ways, although group boundaries were accentuated by Belgian colonial policy. Genetic and ethnohistoric evidence points to the Tutsi being a an offshoot of the great migration of Nilotic cattle-herders over the last millennium, while the Hutu derive ultimately from an even greater demic expansion, of the Bantu. The Tutsi came to speak the same language as the Hutu, and there has been some intermarriage between the two populations, but they are still physically fairly distinct from one another, with the Tutsi taller and thinner. These physical differences played into the development of ethnic animosity, an instance of “somatic prejudice.” A big theme of anti-Tutsi propaganda in the period leading up to the genocide is that Tutsi women were especially sexually alluring, but also wanton, dangerous, and emasculating. A few story titles, “Beautiful Tutsi Women as Bait into Servitude” and “The Death Trap of Tutsi Women’s Beauty,” make the point (as did a lot of visual pornography). In the Hutu Ten Commandments, a major piece of anti-Tutsi propaganda published in 1990, the first three commandments are concerned with getting Hutu men to resist the allure of Tutsi women. Sexuality and ethnicity are the source of some of our most intense emotions; together they make an especially combustible combination.

The world at 1000 BCE

Here’s a quick look at the world around 1000 BCE

The world population is about 50 million.

The Bantu expansion is just beginning, from a homeland on the present Nigeria/Cameroon border. It will eventually cover most of Africa south of the equator. The expansion is sometimes told as a story of first farmers replacing hunter-gatherers. But, as with the Indo-European expansion, this now looks to be too simple. Other farmers and herders reached east Africa before the Bantu; traces of their languages survive as eastern Bantu substrates. So the Bantu had something extra – social organization? malaria resistance? – going for them.

Seafarers with roots in the Lapita culture have already reached Western Polynesian – Samoa and Tonga, previously uninhabited.

The Olmec are flourishing in Meso-America. A controversial find (the Cascajal block) suggests they are just taking up writing.

In China, the Mandate of Heaven has passed from the Shang Dynasty to the Zhou.

In the Near East and Eastern Mediterranean, the Late Bronze Age collapse has opened up space for smaller states. Tyre and other Phoenician city-states are sailing the Mediterranean. Phoenicians are using an alphabet that Greeks will eventually adapt. There might be other borrowings: Odysseus might originally have been Phoenician. At least that was the argument of the early twentieth century French diplomat and classicist Victor Bérard. He thought that Homer had folded an earlier Phoenician picaresque tale into his epic. James Joyce was very taken with this theory; Joyce’s Levantine Leopold Bloom owes something to Bérard’s Phoenician Odysseus.

Further south, Philistines and Israelites have been duking it out, with Israelites gaining the upper hand under David* (king from 1010 to 970 BCE). The Iron Age conventionally begins now, with the widespread use of iron – more abundant and cheaper than bronze.

On the steppe, horses have long been domesticated, but people are now learning to make effective use of cavalry – fighting in formation and firing volleys from horseback. This is the beginning of 2500 years in which the division between Steppe and Sown will be central to Eurasian history.

* Everybody knows that David killed Goliath (1 Samuel 17). However, according to 2 Samuel 21:19, Goliath was killed by Elhanan of Bethlehem. (Depending on which version of the Bible you use, the victim might be given as the brother of Goliath, but the italicised bit is a later interpolation. It’s plain Goliath originally.) Probably the Elhanan story is the original one, and the whole David-and-Goliath story amounts to later resume-padding on the part of David at the expense of a subordinate. See The Historical David: The Real Life of an Invented Hero for this and other demonstrations of how we can recover likely truths from historical texts.

Think like an Egyptian

2560 BCE

You might think that with the Egyptian pyramids being famous for thousands of years (they’re the only one of the Seven Wonders of the Ancient World still standing) there wouldn’t be much new to say about them. But you’d be wrong. The Egyptians wrote down virtually nothing about their architectural methods; they may have worked with some kind of 3-D models – the Bronze Age version of Computer-Aided Design – rather than anything like blueprints. So we haven’t really known much about how the pyramids were built. In particular, it’s been a real puzzle how they moved building blocks to near the top of the pyramid in the later stages of construction. If blocks were moved along a straight ramp up the side of the pyramid, the ramp in the last stages would have had to be a mile long, and contained as much material as the pyramid itself. It also wouldn’t have fit on the Giza plateau. Recently, Jean-Pierre Houdin, a French architect, may have figured out how the problem was solved in the case of the largest pyramid, the Great Pyramid built for King Khufu (Cheops). According to Houdin, the builders used an external ramp for the early stages of construction. But they also built a vaulted internal ramp, spiraling around insidethe pyramid, and moved blocks up it for the later stages. (And the builders economized by dismantling the external ramp and using it for construction material.) Houdin revealed his theory in 2005. Both before and since then he has put a huge amount of work into understanding how the Great Pyramid was built. For example, he may also have come up with an explanation for the 150 foot-long, narrow, slanting Grand Gallery in the pyramid: it looks like it was used to run counterweights on a trolley that helped to bring up some of the heaviest stones, the granite blocks used to reinforce the King’s Chamber.

African geneses

303 – 2.88 thousand years ago

Our picture of human evolution in Africa around 300 thousand years ago has changed dramatically in just the last few years.

Here’s something we already knew. This skull was found at Broken Hill, Zambia, in 1921, He (yes, “he,” he’s probably male) is sometimes known as Rhodesian Man. He looks like he’s a step away from Homo erectus, but not quite Homo sapiens. He’s heavily built, with massive brow ridges. (He looks like he could pass the “pencil test” for erectus: you could rest a pencil on those ridges. Of course, seriously, this isn’t enough to define a species.)  But he’s got a flat face and relatively large brain. He could be significantly younger than 300,000 years ago.

But now Rhodesian Man is bracketed both geographically and evolutionarily by some new finds. From Jebel Irhoud, Morocco, around 315 thousand years ago, come these skulls, which are more unequivocally Homo sapiens. pushing the fossil record of our species back 100 thousand years. The skull is still archaic – elongated rather than globular like a modern human – but the face is now tucked under the skull, as it is with us. The brow ridges are not as pronounced as with Rhodesian man, although still heavy for modern Homo sapiens.

And we now have dates for Homo naledi, from South Africa, of 335-236 thousand years ago. This recently discovered species had a tiny brain, and may have been adapted for climbing trees, but still makes it into genus Homo based on other features (teeth and jaws, lower skeleton). The initial guess from a lot of folks was that this was a very early member of our genus, somewhere around early Homo erectus or earlier. But instead, Homo naledi looks to have been around at the same time as early Homo sapiens.

In other words, Africa 300,000 years ago was home to an impressive variety of humans – archaic Homo sapiens in Morocco, near relations in Zambia, and barely-humans in South Africa.

Amplifier lakes

1.83 – 1.74 million years ago.

(Posted a day late)

We’re now counting off past time at the rate of 100,000 years a day.

Paleontologists and paleoanthropologists are busy sorting out what was special about the climate and ecology of Africa, especially East Africa, that contributed to various phases of hominin evolution. (“Hominin” is the current label for everyone more closely related to us than to our closest living relatives, i.e. chimpanzees and bonobos. My spell checker wants me to change it to hominid, the old label.) For example, Elizabeth Vrba, a South African paleontologist, argued that about 2.5 million years ago East Africa experienced a “turnover pulse” that affected a number of species. As the climate shifted toward cooler weather, and grasslands expanded, there was a wave of extinction and speciation among antelopes and (arguably) hominins as well.

More recently, paleoanthropologists have argued that not just cooling or aridity per se, but climate variability played a major role in driving hominin evolution, with episodes of greater variability leading to various responses ­– extinction, habitat tracking, or greater behavioral flexibility – as suggested in the diagram below.

More specifically, it looks like there were particular times when lakes were flickering in and out of existence along the Eastern and Western arms of the East African Rift Valley. Between just under 3 million years ago and just under 1 million three episodes stand out: around 2.7-2.5 mya, 1.9-1.7 mya, and 1.1-0.9 mya. These happen at intervals of 800,000 years, and may be tied to very long cycles in the eccentricity of Earth’s orbit. Within each of these episodes, the Rift Valley was home to large numbers of “amplifier lakes.” These lakes formed briefly during short intervals of high precipitation, and then evaporated quickly, making for a rich (sometimes) but also a particularly challenging environment.

Tellingly, it looks like these episodes were also associated with important events in hominin evolution. of 15 hominin species that evolved in this period, 12 appeared during these episodes.

This story, and much more, are set out in Lewis Dartnell’s excellent recent Origins: How Earth’s History Shaped Human History. However it is a ways from being settled science: here is a review of some of the problems with identifying ecological drivers of human evolution (behind a paywall unfortunately). The coauthors include some of my colleagues at the University of Utah.

Two Million BC

2.04 – 1.94 million years ago

Two million years ago, there were multiple hominin species in Africa. There was Homo habilis, with a larger brain than any australopithecine, but similar body size and long arms. There was also the recently discovered Australopithecus sediba, with brain not especially large, but maybe reorganized in a human direction, and teeth trending human-wards as well.

A. sediba

There were two robust species that we know of, boisei in east Africa and robustus in southern Africa. The robusts had huge premolars and molars, and enormous jaw muscles running through a large zygomatic arch to attach all the way up to the sagittal crest in the middle of the skull. Gorillas have sagittal crests too, but with them it’s about powerful bites from incisors and canines. You, on the other hand, don’t have a sagittal crest. Your temporalis muscle only runs up to your temple.

The robusts are sometimes given their own genus Paranthropus, other times included in Australopithecus. This reflects uncertainty about their relationships. Did robust morphology evolve once, with both boisei and robustus evolving from aethiopicus? Or did it evolve independently several times, with robustus evolving from Australopithecus africanus in southern Africa?

And remarkably, we now know that three different hominin genera were around not just at the same time and but in the same place, hanging around a South African cave system: Paranthropus robustus, plus Australopithecus africanus (an old-timer, with more than a million year past behind her),  plus Homo erectus (a newcomer, with a more than a million year future ahead of her).

Ardi

4.4 Mya

We’ve got earlier hominins – Sahelanthropus, Orrorin tugensis, even an earlier species of Ardipithecus – but Ardi (her nickname, her species is Ardipithecus ramidus) stands out because she left us an exceptionally complete skeleton. 

And she helped to upend a lot of theories based on drawing a straight line between modern chimpanzees and later australopithecines. She was a biped. Her legs tucked under her pelvis, with a short lower spine, and a broad pelvis (all closer to modern humans than to chimps). Her outer foot was adapted for walking on the ground. But her toes were long-ish. And her big toe stood way off to the side: well-adapted for grasping branches. So when she was walking on the ground, she had to use her second toe to push off, instead of – like you and me – her big toe.

Ardi really shifted people to realizing that gorillas and chimps are specialized beasts, specialized in being big apes adept at climbing trees, grasping branches, swinging around, and pulling themselves up by their arms, but paying a price in inefficient knuckle walking when down on the ground. Ardi was taking up a different specialization, still a tree climber (her habitat was woodland, more than savannah), but ambling around (not quite striding yet) two-legged on the ground. 

So the common ancestor of chimps and humans, back before Ardi, apparently didn’t look all that much like either. In some respects she might have been somewhat closer to humans. She might even have been a sometime biped on the ground.

For a great recent summary, including lots of information about Ardi, and also about the politics, academic and otherwise, of digging fossils, check out Fossil Men: The Quest for the Oldest Skeleton and the Origins of Humankind.

Toumaï

7.04 – 6.67 million years ago

Sahelanthropus is a 7-6 million year old species whose remains have been found in Chad. “Toumaï” (“hope of life” in the Daza language) is the nickname for one individual, represented by a fairly complete skull. Otherwise Sahelanthropus is known from some jaws and teeth.

One of the things that distinguishes hominins (the human line) from great apes is that the front teeth – canines and incisors – are reduced. (Back teeth are another story. They stay big, or even get bigger, for a long time.) By this standard, Sahelanthropus looks like an early hominin. It’s got reduced incisors and canines and a short mid-face. And depending on who you talk to, it might or might not have been bipedal, although the foramen magnum (where the spine enters the skull) was maybe not positioned to balance the skull on top of the spine. Not that there was much brain inside the skull: the cranial capacity (maybe 360 cc) would be at the low end for a chimp.

So Sahelanthropus could be one of the very first species related to us after the chimp/human split. Chad, where Sahelanthropus was found, is a long way from East Africa, where most other hominins have been found, which suggests there may have been a profusion of hominins across Africa, waiting to be discovered.

The face in the Logarithmic History banner for the month of May is a Sahelanthropus.