In 2004, anthropologists discovered fossils of tiny human ancestors on an Indonesian island. Called micropygmies, they were about three feet tall. Their brains were smaller than chimpanzee brains. They appeared to be descended from Homo erectus rather than Homo sapiens.

They survived until about 20,000 years ago — which was impressive, since Homo sapiens reached nearby islands about 50,000 years ago. Why didn’t the Homo sapiens kill off the micropygmies? Jared Diamond was puzzled by this:

The discoverers of the Flores micropygmies conclude that they survived on Flores until at least 18,000 years ago (1, 2). To me, that is the most astonishing finding, even more astonishing than the micropygmies’ existence. We know that full-sized H. sapiens reached Australia and New Guinea through Indonesia by 46,000 years ago, that most of the large mammals of Australia then promptly went extinct (probably in part exterminated by H. sapiens), and that the first arrival of behaviorally modern H. sapiens on all other islands and continents in the world was accompanied by similar waves of extinction/extermination. We also know that humans have exterminated competing humans even more assiduously than they have exterminated large nonhuman mammals. How could the micropygmies have survived the onslaught of H. sapiens?

One could perhaps seek a parallel in the peaceful modern coexistence of full-sized sapiens and pygmy sapiens in the Congo and Philippines, based on complementary economies, with pygmy hunter-gatherers trading forest products to full-sized sapiens farmers. But full-sized sapiens hunter-gatherers 18,000 years ago would have been much too similar economically to micropygmy hunter-gatherers to permit coexistence based on complementary economies and trade. One could also invoke the continued coexistence of chimpanzees and humans in Africa, based on chimps being economically too different from us to compete (very doubtful for micropygmies), and on chimps being too dangerous to be worth hunting (probably true for micropygmies). Then, one could point to the reported survival of the pygmy stegodont elephants on Flores until 12,000 years ago (1, 2): If stegodonts survived so long in the presence of H. sapiens, why not micropygmies as well? Finally, one might suggest that all of the recent dates for stegodonts and micropygmies on Flores are in error [despite the evidence presented in (1) and (2)], and that both stegodonts and micropygmies became extinct 46,000 years ago within a century of H. sapiens‘ arrival on Flores. All of these analogies and suggestions strike me as implausible: I just can’t conceive of a long temporal overlap of sapiens and erectus, and I am reluctant to believe that all of the dates in (1) and (2) are wrong. Hence I don’t know what to make of the reported coexistence.

Yes, I know, when you have a hammer everything looks like a nail. But I think Diamond is quite wrong about the nature of Homo sapiens economies 50,000 years ago. To Diamond, the big change was the invention of agriculture. Before that, hunter-gatherer; after that, farmer and occupational specialization. I believe there were vast economic changes long before agriculture — it took a long time to evolve language, and that didn’t start until there was already plenty of trading. By 50,000 years ago, I’m sure there was lots of specialization (Person A makes/knows X, Person B makes/knows Y), giving the Homo sapiens all sorts of tools and other useful expertise that the micropygmies didn’t have. They both hunted and gathered but much larger brains and a vast amount of expertise would have been for naught if they didn’t hunt and gather different foods. Homo erectus did not have anything like human language, as far as I can tell; therefore they didn’t have lots of trading or expertise. The two groups could co-exist because their foods were different. I suspect the H. sapiens, able to hunt really large animals, thought small animals, which supported the micropygmies, a waste of time.