Newly discovered ancient bones may reshape our understanding of human evolution.
Two previously unknown lineages of humans may have been identified from a hip bone found in a French cave and a skull found in China.
Lineages we know
Apart from anatomically modern humans, Homo sapiens, two other now extinct human lineages are known: Neanderthals and Denisovans.
Neanderthals emerged in Africa roughly 300,000–400,000 years ago and spread to Europe where they had adapted to the cold, harsh conditions during the last Ice Age. Neanderthal remains disappear from the fossil record about 40,000 ago.
Denisovans are a recent addition to the human family tree. This ancient lineage was unknown until the first Denisovan remains were discovered in Siberia in 2010. It is believed this group of humans shared a common ancestor with Neanderthals. While the Neanderthal lineage migrated north to Europe, the Denisovans emerged from a group that spread eastward out of Africa into Asia. Denisovans may have lived until as recently as 30,000 years ago.
New piece of the puzzle in China
Anatomically modern humans first appeared in China 120,000 years ago.
The 300,000-year-old skull unearthed in Hualongdong in eastern China suggests that another human lineage sharing some of our ‘modern’ features may have emerged even earlier in Asia. Analysis of the fossils are described in a paper published in the Journal of Human Evolution.
It has previously been suggested that a fourth unknown human group might have existed in Middle to Late Pleistocene (roughly 800,000 to 12,000 years ago) based on genomic studies on Neanderthal remains in Europe and western Asia. The Chinese skull might be a missing piece of this puzzle.
The bones belonged to a 12 or 13 year-old. While showing some modern human-like features, the limbs, skull cap and jaw “seem to reflect more primitive traits” according to the authors. The mosaic of features in the ancient individual suggests the coexistence of three lineages in Asia – H. erectus, Denisovans, and this other lineage which appears to be “phylogenetically close” to modern humans.
Mystery in France
A more recent example of a potential “other” lineage of human was found in the French cave Grotte du Renne.
The hip bone, or ilium, is from a newborn baby and dates to about 42,000 years ago. It is roughly this time which saw the appearance of modern humans in central Europe, eventually replacing the Neanderthal population.
In a study published in Nature, researchers analysed the ancient ilium. Comparing the ilium from Grotte du Renne with 2 other Neanderthal ilia and 32 modern hip bones from modern newborns, the researchers concluded that “it clearly differs from the Neanderthals.”
“We propose that this is due to its belonging to an early modern human lineage whose morphology differs slightly from present-day humans,” they continue. The ilium’s shape falls outside the normal bounds of variation in modern humans.
Grotte du Renne has been the subject of archaeological research for decades. Deeper layers within the cave show it was occupied by Neanderthals. Higher layers indicate the presence of anatomically modern humans.
Between those layers, is a period which appears to show the two hominins coexisting. Stone tools referred to as Châtelperronian techno-cultural complex are found in this layer, though it is unclear if they were produced by Homo sapiens or Neanderthals.
The researchers explore multiple possibilities including the production of the tools by Homo sapiens, later copied by Neanderthals, or that they were made by an as yet unknown lineage of ancient human, possibly represented by the anatomically distinct ilium.
While yet to be confirmed by further research, potential unknown lineages suggest a much more complicated path to the modern human than previously thought.
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