The Accidental Species: Misunderstandings of Human Evolution Read Online Free
Author: Henry Gee
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 thebasis 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 commonclose 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
—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 thebasis 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 commonclose 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
Readers choose
Ellie Bay
S. M. Bowles
Lawrence Block
Nicki Elson
J. J. Newman
Heather Rainier
Hal Clement
Cassandra Zara, Lucinda Lane
CRYSTAL GREEN
Dyan Sheldon