Apes’ inner ears could help scientists reconstruct the early branches of the human family tree and identify the last common ancestor from which we evolved
- Researchers compared the bony inner ear structures of 27 primate species
- These included humans and gorillas as well as extinct apes and Australopithecus
- They found that ear structure similarities indicate evolutionary relationships
- Further studies with other fossil specimens will be needed for firm conclusions
Apes’ inner ears could help scientists reconstruct the early branches of the human family tree and identify the last common ancestor from which we evolved.
Used in both balance and hearing, the bony cavity that houses the inner ear is often preserved in the fossil record.
Its changing shape across species has helped experts track the evolution of certain mammals, but it was not previously clear if the approach could be used with apes.
According to the researchers, comparing inner ear bones could help could help us better understand the evolution of humans and our relationship to other hominoids.
The ‘hominoidea’ are the collection of higher primates that includes humans, chimpanzees, gibbons, gorillas and orangutans, their ancestors and close relatives.
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Apes’ inner ears could help scientists reconstruct the early branches of the human family tree and identify the last common ancestor from which we evolved. Pictured, a 3D model of a gibbon’s skull, with the inner ear highlighted in red
In their study, palaeontologist Alessandro Urciuoli of the Institut Català de Paleontologia Miquel Crusafont (ICP) in Barcelona, Spain and colleagues used 3D imaging to study the bony inner ear cavities of 27 species of monkeys and apes.
These included both humans and fossils of the extinct ape Oreopithecus and the fossil hominin Australopithecus.
‘Reconstructing the evolutionary history of apes and humans and determining the morphology of the last common ancestor from which they evolved are challenging tasks,’ said Mr Urciuoli.
‘While DNA can help evolutionary biologists work out how living species are related to one another, fossils are typically the principle source of information for extinct species, although they must be used with caution.’
The researchers found that the variations in the shapes of the inner ear structures did most closely reflect the evolutionary relationships between the different primate species — and not, for example, factors like how each animal moves.
The team went on to identified the different features of the bony chambers that were shared across different ape groups and estimated how the inner ears might have looked in these group’s ancestor.
Analysis supported both the idea that Australopithecus was more closely related to modern humans that to other apes and that Oreopithecus was a more primitive species of ape than those alive in the present day.
Used in both balance and hearing, the bony cavity that houses the inner ear is often preserved in the fossil record. Its changing shape across species has helped experts track the evolution of certain mammals, but it was not previously clear if the approach could be used with apes
In their study, palaeontologist Alessandro Urciuoli of the Institut Català de Paleontologia Miquel Crusafont (ICP) in Spain and colleagues used 3D imaging to study the bony inner ear cavities of 27 species of monkeys and apes. These — 16 of which are pictured — included both humans and fossils of the extinct ape Oreopithecus and the fossil hominin Australopithecus
‘Our work provides a testable hypothesis about inner ear evolution in apes and humans,’ said paper author and Institut Català de Paleontologia Miquel Crusafont director David Alba.
This hypothesis, he added, ‘should be subjected to further scrutiny based on the analysis of additional fossils, particularly for great apes that existed during the Miocene.’
The Miocene geological period — which spanned from 23–5 million years ago — is when the evolutionary path that led to the hominoids, or apes, became distinct.
Untangling the nature of the relationships between Miocene apes will be key to understanding the evolution of humans and our closest living relatives, the bonobos and the chimpanzees.
Late last year, a study by researchers from the United States revealed the existence of a 12-million-year-old ‘missing link’ between humans and our ape-like ancestors.
The creature, Danuvius guggenmosi, was a broad-chested primate that lived in what is today mountainous Allgäu region of Bavaria, Germany.
D. guggenmosi, experts found, had arms suited to hanging from trees but straight legs like us that would have served it well walking upright.
The full findings of the latest study were published in the journal eLife.
WHEN DID HUMAN ANCESTORS FIRST EMERGE?
The timeline of human evolution can be traced back millions of years. Experts estimate that the family tree goes as such:
55 million years ago – First primitive primates evolve
15 million years ago – Hominidae (great apes) evolve from the ancestors of the gibbon
7 million years ago – First gorillas evolve. Later, chimp and human lineages diverge
A recreation of a Neanderthal man is pictured
5.5 million years ago – Ardipithecus, early ‘proto-human’ shares traits with chimps and gorillas
4 million years ago – Ape like early humans, the Australopithecines appeared. They had brains no larger than a chimpanzee’s but other more human like features
3.9-2.9 million years ago – Australoipithecus afarensis lived in Africa.
2.7 million years ago – Paranthropus, lived in woods and had massive jaws for chewing
2.6 million years ago – Hand axes become the first major technological innovation
2.3 million years ago – Homo habilis first thought to have appeared in Africa
1.85 million years ago – First ‘modern’ hand emerges
1.8 million years ago – Homo ergaster begins to appear in fossil record
800,000 years ago – Early humans control fire and create hearths. Brain size increases rapidly
400,000 years ago – Neanderthals first begin to appear and spread across Europe and Asia
300,000 to 200,000 years ago – Homo sapiens – modern humans – appear in Africa
50,000 to 40,000 years ago – Modern humans reach Europe