The Accidental Species: Misunderstandings of Human Evolution (3 page)

To emphasize the strangeness of the creature, the discoverers gave it a scientific name that was noncommittal, yet set it apart from anything discovered hitherto. They called it
Sundanthropus florianus
—the Man from Flores, in the Sunda Islands. However, the panel of experts I called on to comment on the draft paper, and to make suggestions for its improvement, pointed out how relatively modern the skull looked—how much it looked like our own genus,
Homo
. One commentator also noted that “florianus” didn’t actually mean “from Flores” so much as “flowery anus.” Clearly, some revision was required.

When the revised paper was published in October, the creature had become
Homo floresiensis
—Flores Man. The skeleton with its skull was catalogued as LB-1, but the media were quick to catch on to a suggestion of one of the discoverers that it should be known as the “Hobbit,” after the diminutive hole-dwellers of J. R. R. Tolkien’s fiction—though we in the
Nature
office sometimes referred to her as “Flo” (the skeleton having been described as that of a female).

The paper—and the several commentaries that appeared in its wake—saw the Hobbit as a member of a race of humanlike creatures that had evolved in isolation, on Flores itself or nearby, perhaps descendants of the full-sized toolmakers known to have been on Flores for as long as a million years. If isolation on islands could do strange things to creatures as varied as birds and elephants, lizards and tortoises, there seemed no reason in principle why hominins should be exempt. The Hobbit could easily be seen as a relative of
Homo erectus
, known from remains on mainland Asia to be almost as tall as a modern human—but dwarfed as a result of isolation, alongside the elephants whose island it shared.

And then the fun started.

Hardly had the ink dried on the first account of the Hobbit when the backlash began.
¹³
Critics were exercised by two particular aspects of the discovery.

First, that such an archaic-looking creature had existed so recently, in a region already long inhabited by modern humans.

Second, that a creature with such an incredibly tiny brain could have made tools. The brain was so tiny, even in proportion to the tiny body,
that the Hobbit must—the critics reasoned—have been suffering from a physical or genetic abnormality.

Although criticism of the find came in various shades, critics were united, more or less, in proposing an alternative scenario for the existence of the Hobbit. Rather than it being a distinct species, a relic of an older world preserved out of time, it was a form of modern human suffering from microcephaly, a congenital disorder that produces midgets with abnormally small heads.
¹⁴

The first objection can be seen as a symptom of human exceptionalism, the erroneous yet deeply ingrained tendency that I seek to explode in this book. That is, the tendency to see ourselves as the inevitable culmination of a progressive trend of advancement in evolution. The discovery of such a primitive-looking creature living on the same planet at the same time as
Homo sapiens
challenges that view. It is a perhaps unfortunate fact that the only hominin that still exists on Earth is our own. This fact rather reinforces the idea that various species of hominin—the “missing links”—each more humanlike than the one before, succeeded one another with the planned inevitability of runners in a relay race, and that it is not somehow possible for several species of hominin to coexist on the same planet.

It was not always so. As recently as 50,000 years ago, there were at least four different kinds of hominin on Earth—
Homo sapiens
in Africa, Neanderthals (
Homo neanderthalensis
) in Europe and western Asia, and
Homo erectus
in southeastern Asia, to which must now be added the obscure “Denisovans” from eastern Asia.
¹⁵
The addition of a fifth—
Homo floresiensis
—would, in such circumstances, hardly be a surprise: neither should it be a surprise were yet more distinct forms of human to be discovered. Indeed, the only period in which only one species of hominin walks the earth is right now. Modern times are the exception, not the norm.

That different hominins might live together in the same region should, likewise, not be a surprise. It is known that various kinds of early
Homo
coexisted with australopiths in east Africa between 2 and 3 million years ago, and that humans and Neanderthals coexisted in Europe for at least 10,000 years (between around 41,000 and 27,000 years ago). The survival of Neanderthal genes in the modern human population
¹⁶
shows that the two species occasionally interbred. There can, therefore, be no objection to
Homo floresiensis
as a distinct species, simply on the
basis that modern humans were around at the same time; nor on the basis that
Homo floresiensis
looks too primitive to have survived until modern times. As anachronisms go (what people like to call “living fossils”), the Hobbit is hardly a world-beater. Go tell it to the tuatara of New Zealand, the last relic of a lineage of reptiles distinct from a time before dinosaurs evolved, and hardly changed in its external appearance for 250 million years.
¹⁷

The second objection—that the very small brain of
Homo floresiensis
must have been pathological, a symptom of microcephaly—is likewise flawed, but much more interesting.

Microcephalics have heads that are disproportionately small, even for very small people, such as dwarfs or pygmies. It is important to realize that microcephaly has a number of distinct causes. Microcephaly is not one single disorder. Microcephalics suffer from a variety of other disorders as well as malformations of the skull, face, and limbs, the particular suite of complaints dependent on the variety of microcephaly at issue. Some degree of mental retardation is, perhaps not surprisingly, a feature common to microcephalics in general.

And so it was that the Hobbit was compared with various kinds of microcephalics. However, although the brain of the Hobbit is undoubtedly very small, and the skull and skeleton of LB-1 strange in many ways, its strangeness could not be mapped easily onto any variety of microcephaly recorded for modern humans. That does not mean that the microcephaly idea is ruled out. It could be that LB-1 is the only known exemplar of a hitherto unknown variety of microcephaly. After all, microcephaly of any kind is rather rare, so much so that scientists seeking to compare the Hobbit with microcephalics had to dig deep into the world’s medical museums and medical literature even to find the very few specimens of microcephalics available for examination. It is possible that LB-1 suffered from a variety of microcephaly as yet unmapped.

Perhaps the most interesting suggestion of this sort—that LB-1 was a pathological specimen of modern human—was that it was not a microcephalic, but a cretin.
¹⁸
Cretinism is not a genetic or inherited disorder, but the result of a chronic deficiency of iodine in the diet. Iodine is a vital component of a hormone, thyroxine, which the body needs for proper growth. Without thyroxine, growth is retarded, and the result is short people, with small heads and various degrees of mental impairment. Iodine is found in seafood, so cretinism is not common
close to the sea. It is (or was), however, more common in isolated, inland communities. Liang Bua is in the Floresian hinterland, relatively far from the sea. It is conceivable that LB-1 could have belonged to a tribe of highlanders more prone to cretinism than fisherfolk living on the coast.

But the more that
Homo floresiensis
was studied, especially once the peculiar proportions of its arms and feet became better known, the less well it fit into any known variety of pathology found in modern humans.
¹⁹

The scenarios in which
Homo floresiensis
was not a real species but a pathological version of a modern human were varied, but had one aspect in common: they failed to emphasize (or even mention) that LB-1 wasn’t an isolated case that could be singled out as pathological. Remains of the same kind of creature had been recovered from strata at Liang Bua representing an enormous span of time, back to a time before modern humans were known to have existed in the region. This fact alone should have been enough to question any idea that
Homo floresiensis
was a pathological offshoot of modern humans.

The fundamental problem with the microcephaly idea lies less with the idea of microcephaly, or pathology, than that its proponents subscribe to an untenable view of human evolution—one that can only admit to a single pathway of evolution in which human beings stand at the head of a single line of ancestors, each one progressively improved compared with the one before. In that worldview, Flo can
only
be a human being—in which case one then has to explain how she came to look so odd. Proponents of this view tend to be both passionate and argumentative, and become more so as evidence mounts to discredit it. This suggests that the argument is less about one curious fossil than an attempt to shore up a view of the world that is fundamentally mistaken.

The same problem besets the assertion that as a consequence of its small brain,
Homo floresiensis
would not have been able to make tools. It is now known that a wide variety of animals can make tools, many of a sophistication to rival anything made by early hominins. Some of these creatures have very small brains indeed—brain size per se need have little or no connection with technical ability. The idea that brain size matters comes from the view that human evolution is progressive, linear, and inevitably improving.

The problem remained, however, that irrespective of its origins,
Homo floresiensis
really did have a disproportionately tiny head. Scaling a modern human down to Hobbit size would have created a creature with a tiny head, but only if it were pathological. The heads of
Homo erectus
were, in contrast, smaller than those of
Homo sapiens
, so perhaps
Homo floresiensis
would be better seen as a dwarfed (but nonpathological)
Homo erectus
.
Homo erectus
was a remarkably variable species with perhaps a tendency to smallness,
²⁰
something that might play in its favor as a possible ancestor of
Homo floresiensis
. Specimens found in the Republic of Georgia dated to around 1.7 million years ago seem to represent a sample of
Homo erectus
of a primitive, early kind.
²¹
These creatures were small, some comparable in size with
Homo floresiensis
, but their brains were at least twice the size of LB-1. Shrinking
Homo erectus
down to the size of
Homo floresiensis
would still produce a creature with too large a brain. Flo had to have evolved from something smaller still.

Two possible solutions presented themselves. One was a study on island dwarfism in now-extinct hippopotamuses that lived on Madagascar, showing that in some cases, the brains of animals subject to island dwarfism would be reduced more than one would expect, even when one scaled a full-sized animal down to midget size.
²²
This makes sense in terms of energetics. A possible cause of island dwarfism is that castaways evolve a smaller size in response to the pressure of reduced resources. The brain is, proverbially, the most expensive organ to run in terms of its mass, and so might be expected to evolve a disproportionately small size. Yet such a reduction has its limits. A brain can’t reduce to the extent that function would be impaired. However you look at it, a race of cretins or microcephalics isn’t going to survive for very long. But even when the further downsizing of brains of island species was accounted for, the brains of
Homo floresiensis
looked too small, even for
Homo erectus
.

The second solution was that
Homo floresiensis
was a dwarfed version of an even earlier, more primitive hominin than
Homo erectus
, perhaps a creature so primitive that it would not be grouped within the genus
Homo
. This had indeed been an option favored by the original discovery team, but they had to some extent been dissuaded by the panel of experts I’d assembled to assess the original report, who had looked at the skull of LB-1 and said that despite its size it fit better within
Homo
rather than outside it.

After all, what choice was there? It seemed far simpler to admit a new member to our own select genus, no matter how weird the entrant,
than to defy everything we thought we knew we knew about the human story: to open the floodgates of the unknown unknown.

Conventional wisdom suggests that the entire tale of human evolution had taken place exclusively in Africa until around 1.8 million years ago, when
Homo erectus
became the first hominin to leave that continent and colonize much of the rest of the Old World. The fossils from Georgia might have represented this wave of emigration. There is no compelling evidence that earlier hominins, such as
Australopithecus
or the earliest members of our own genus such as
Homo habilis
(somewhat more like
Australopithecus
than
Homo erectus
in many ways) had ever left Africa.
²³
Homo floresiensis
just might be that first piece of evidence.

Perhaps some hominin left Africa long before
Homo erectus
had evolved, migrating across the Old World, evolving into all sorts of diverse and unimagined forms, the only trace of such an adventure being a single, late-surviving relic marooned on remote and distant Flores.

When the researchers unearthed
Homo floresiensis
from its long home, they opened the door to things we not only didn’t know, but didn’t even suspect, so wedded were we to the canonical out-of-Africa picture: not just to a remarkable, almost unbelievable testament to the power of evolution to shape living matter into unexpected shapes; but to a hitherto unknown and unsuspected chapter in human evolution, a vista far greater and more varied than anyone had dreamed possible.