East African Girl Courtesy EthioView

Curious Article No. 10:

I thought I'd tackle a special challenge this week and for the next several by chronicling the saga of Homo sapiens as concisely and as refreshingly as possible. You'll be reading about the sorts of events and discoveries that left significant impacts yet in many cases have gone largely unpublished either because they don't jibe with conventional wisdom or because their news is much too recent.

Now I've had to tunnel my way through hundreds of articles — not a few of which were either contradictory, distressingly abstruse, or both. There’s never a dull moment in history and especially paleoanthropology. They're contentious, emotionally charged fields of towering egos and sociopolitical agendas. Some of the earliest paleontologists would go so far as to smash bones to keep them out of the hands of their academic rivals. The good news is that the human story is an infinitely more interesting subject now than ever before, owing to a boom in physical discoveries, vastly improved dating techniques, and, of course, DNA sequencing that frequently reveals intriguing surprises. We can now look at our last 200,000 years from a perspective that was previously impossible.

I can't guarantee 100% accuracy of the assertions or dates that follow. Sometimes I had to choose what I felt was the most convincing of two or more competing claims, while at others when multiple versions seemed equally plausible I'd split the difference. Years occurring well Before the Common Era (such as 1000 bce or 3005 bp) are mostly approximate, but to avoid having to say “at around” all the time I'll pretend they're exact. Researchers will undoubtedly refine these details as more data comes in, but I expect that the general scheme below is probably close enough to the truth by now that it won't change appreciably.

Six million years before present (bp), Ardipithecus ramidus and Orrorin tugenensis, so far the earliest known bipedal hominids, were living in eastern Africa. Right now it appears that we either descended from tugenensis or at least shared a close common ancestor. At 5.4 million bp the Gibraltar land bridge broke with little warning and allowed the Atlantic to roar through and permanently flood a vast desert basin, turning it into the Mediterranean Sea. In 200,000 bp the first Homo sapiens appear in the fossil record, just north of Lake Victoria. Over a dozen other hominids, including the two above, had preceded us by hundreds of millennia and had spread throughout much of the Old World by that time. In 150,000 we expanded through central and southern Africa and to the east coast at the mouth of the Red Sea. The so-called mitochondrial Eve, from whom all of us matrilineally descend, lived at this time.

Hominids in Eurasia (we weren't there yet) first domesticated dogs from gray wolves as far back as 135,000 bp. Among the oldest surviving breeds are the dingo, Carolina dog, and New Guinea singing dog. A glacial maximum occurred in 130,000. Since we were still in Africa it didn't affect us directly, though the cooler temperatures may have hampered our food supplies. In 125,000 one human clan followed the Nile northward and up the east Mediterranean coast; but something happened and within 35,000 years (around 90,000 bp) they had all died off. At that point a second party left Africa, this time instead crossing to the southern tip of the Arabian peninsula. They followed the seacoast eastward, rounding India, looping down into the Malay Archipelago and then continuing up the Pacific coast into China. Along the way they probably encountered at least two other hominids, Homo erectus and the diminutive Homo floresiensis (Flores Man).

At 74,000 bp the Toba supervolcano exploded in Sumatra with the force of 1.5 million Hiroshima bombs and with a sound level exceeding, according to some estimates, 320 dB or 30 billion space shuttle liftoffs. It blasted 700 cubic miles (2800 cubic km) of magma into the air, which blotted out the sun and lowered temperatures globally. From space, the earth probably looked like a solid gray ball. Most humans and animals who survived the eruption itself either starved or froze to death over the ensuing months and years. The blast deforested much of south-central Asia and buried India under up to 20 feet (6 meters) of ash. We now know from a conspicuous DNA bottleneck that only a few thousand of us made it. Most who survived were in protected areas in Africa, but a handful somehow managed to tough it out in Asia. This was the greatest disaster our kind ever confronted, but we've only understood this recently.

University of Zürich Neanderthal Child Reconstruction

Over the next 9000 years the Asian survivors rebounded and spread into Australia (one Aboriginal skeleton there dates reliably to 62,000 bp) and westward back toward India. Between 65,000 and 52,000 the global climate warmed and humans filled India and spread up through Mesopotamia into the Caspian area and Asia Minor. All during this time we also coexisted with a third hominid species, the Neanderthals. They looked very much like us but were relatively chinless, much more robust, and spoke with a higher and more nasal voice. We also know that they played flutes carved of bone.

Between 52,000 and 45,000, as the climate cooled again, some of us migrated westward through southern Europe and down through the Iberian peninsula. Today’s Basques probably descend from that group. Also at around this time, a meteor weighing roughly 300,000 tons slammed into northern Arizona at around 30,000 miles per hour (13,000 meters per second) to create Barringer Crater; but there were no hominids on that side of the world to witness the event and it left no measurable impact in the climate record.

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Text © Peter Blinn 2006