Earlier we saw how much present-day evolutionary biologists needed and wanted to believe that we had found a new human species in Flores man a decade ago. But it quickly became clear that the ancient inhabitants of Flores were not appreciably different from other humans of their era, apart from very small stature.

The story was different back when Neanderthal skeletons, first unearthed in 1856, began to be studied. As Britannica puts it, “Using those skeletons as a basis, scholars reconstructed the Neanderthals as semi-human, lacking a full upright posture and being somewhat less intelligent than modern humans.” The story grew legs and was admirably suited to demonstrating the fashionable, then-new idea of Darwinian evolution. As a result, “Neanderthal!” is now a term of abuse. The man himself does not protest, of course, for his type is extinct.

Thus, until very recently, Neanderthal man has been explicitly treated as an extinct, separate human species — the status sought for Flores man — in so highly politicized an environment that classification likely depends not on the persuasiveness of facts but the power of factions.

Neanderthal man lived from about 700,000 to about 30,000 years ago, was barrel-chested and well muscled, and had about the same brain capacity as modern man. We have found a variety of his everyday tools, and know some of his habits. But we have very little hard information about his history, apart from the fairly recent line of genetic evidence that Neanderthals and current humans produced children together. There is evidence that a variety of human groups enjoyed intimate relations, including the Denisovans, another group no longer extant, identified recently from a Siberian fossil. The genetic evidence was gleaned from peoples who live outside Africa at present. For example,

Green et al. report that, on average, 1 to 5% of the genomes of non-African individuals are descended from a Neanderthal, and Reich et al. report that 4 to 6% of the genomes of Melanesians are derived from a newly discovered archaic hominin population dubbed the Denisovans.

Some say they were already mingling in Africa. Many now commit themselves to the view that it definitely happened. While the biogeography is fuzzy, some of them speak confidently about the Neanderthal in the family.

Not everyone agrees, of course. Some offer a different interpretation of the genetics, proposing a common ancestor instead. But another study says “none of the usual suspects fits the expected profile of an ancestor of Neanderthals and modern humans,” so the common ancestor is unknown.

Even the richest sites for fossil finds don’t shed as much light as we might hope. The Sima de los Huesos cave in Spain, continuously excavated since 1984, has yielded material for all skeletal regions of at least 28 individuals, including 17 skulls, “many of which are very complete,” spanning about 500,000 years. Some call them “proto-Neanderthals.” Others say they were “part of the Neanderthal clade,” but “not necessarily direct ancestors to the classic Neanderthals.”

Another authority says that current humans and Neanderthals had only brief, limited contact. Another suggests that when pairing did occur, fertile outcomes were less than two percent. Indeed, some say that Neanderthal genes promoted infertility. That said, at least one team claims to have found evidence for a human-Neanderthal hybrid (the unique find should, of course, be treated with caution).

In other words, all we really know for sure is that, as a distinct human type, Neanderthals died out. There is a bonanza of speculation as to why that happened. Some say current humans crowded them out. Others say it was due to interbreeding with current humans (of course, for a minority group, that is a form of crowding out, just not necessarily a violent one). Alternatively, they died before we even got there. Or succumbed to an early industrial revolution. But according to one account, Neanderthals kept us alive precisely because we inherited some of their genes, not that it did them much good.

Some researchers look for physiological clues. Neanderthals tended to have shorter lower legs than modern humans, which helped them move more efficiently in the hills.” But, others point out, they had weaker Achilles tendons, and therefore inferior running ability, which “hits at the crux of why Neanderthals went extinct.” According to some, their large eyes caused their demise (because “more of their brains were devoted to seeing in the long, dark nights in Europe, at the expense of high-level processing”). Apparently, they hung on a while in the Polar Urals in northern Russia. But we really don’t know for sure what happened to them.

Comparisons are difficult. Other distinct types of humans have doubtless died out too, for a variety of reasons. But if they were never classified as separate “semi-human” species that demonstrate the truth of present human evolution theory, speculation as to the cause is bound to be much less widespread, eagerly followed, or contentious.

Obviously, each new find will change the picture of Neanderthal communities a bit, but there is no consistent evidence for them as an “other species.”  One positive outcome of the new uncertainty around Neanderthals’ relationship to current humans has been a reluctance to describe the recently discovered Denisovans as a separate species. Several fossils of this “previously unknown type of archaic human” were found recently in a cave in the Altai Mountains in Siberia.” It turns out that 5 percent of the Denisovan genome survives — not in Siberians but in Papua New Guineans, thousands of miles southeast.

Cautioned perhaps by recent Neanderthal DNA findings and the Flores man episode, researchers have, as a National Geographic article tells us, “been careful not to call Denisovans a new species, opting instead to label them as a Neanderthal ‘sister group.'” And one researcher admitted, “We really don’t know how to equate differences in genome sequences with the species concept.” That’s an important admission and one that will not likely receive the attention it deserves.

As Britannica explains:

Only after World War II were the errors in this perception of Neanderthals [as semi-humans] recognized, and the Neanderthals have since come to be viewed as quite close evolutionarily to modern humans. This latter view has been reflected in the frequent inclusion of the Neanderthals within the species Homo sapiens, usually as a distinct subspecies, H. sapiens neanderthalensis; more recently they have often been classified as a different but closely related species, H. neanderthalensis.

Any decision on that score is bound to be a political one at this point. A separate human species would be so useful, yet it is so elusive. Nature is trying to tell us something that we, or many of us anyway, do not want to hear.

As we saw with Flores man, humans living off unkindly nature by the sweat of their brow, using stone tools, will likely end up living roughly in the same sort of way. But did Neanderthals think? Speak? Create artwork? Some signals are slowly making their way through the noise.

Editor’s note: Here are links to the whole “Science Fictions: Human Evolution” series to date.

Image: Skeleton and reconstruction of Neanderthal man/Wikipedia.