Frank Gaglioti
The discovery of a new human species, Homo luzonensis on the island of Luzon in the Philippines has further highlighted the complexity of human evolution. The findings were published in April in the journal Nature in an article entitled “A new species of Homo from the Late Pleistocene of the Philippines.”
The lead scientist was the archaeologist Armand Mijares from the University of the Philippines, along with scientists from Australia and France.
Mijares found evidence of ancient human activity in the Callao cave located in the north of Luzon in 2003. He was spurred on to dig down to deeper strata after the discovery of Homo floresiensis, commonly referred to the Hobbit due to its diminutive size, on the island of Flores in Indonesia in 2004.
The Callao cave and part of the dig
The breakthrough came in 2007 when Mijares found a foot bone. Subsequent excavations in 2011 and 2015 unearthed two more toe bones, a thigh bone, seven teeth, and two finger bones. The fossils came from two adults and a child and are between 50,000 and 67,000 years old.
“From the beginning, we realised the unusual characteristics of these fossils,” Florent Détroit, a palaeoanthropologist from France’s Musee de l’Homme, told a press briefing. “We completed the comparisons and analyses, and it confirmed that this was something special, unlike any previously described species of hominins in the homo genus,” he said. Hominins include modern humans and all species that are considered ancestral to them.
The scientists conducted a three-dimensional analysis and computer modelling of the bones and found a mixture of modern and more ancient traits. The teeth are relatively small with simple shapes suggesting modern origins, but the upper molar has three roots, an extremely rare trait in modern humans. One of the foot bones is curved, resembling Australopithecines (earlier hominins), and suggesting an arboreal existence as well as walking upright. It is thought that H. luzonensis had a relatively small size, although this is not conclusive due to the lack of larger bones.
Every hominin fossil discovery deepens our understanding of human evolution. It is thought that humans evolved from Australopithecines, known as the southern ape. These emerged in Africa around Ethiopia, Kenya and Tanzania about four million years ago and are known to have survived to two million years ago. Several Australopithecines have been discovered, including A. afarensis that was able to walk upright but still inhabited trees.
A photo of the excavation
The most famous Australopithecine was Lucy, a representative of Australopithecus afarensis discovered in 1974 by Donald Johanson in Ethiopia. Although Lucy had a relatively small brain, the critical development was that she walked upright, freeing the hands for the use of tools. Features such as speech and increased brain capacity evolved later.
The species that is thought to have evolved from the Australopithecines was Homo habilis, first discovered in Tanzania by the famous Kenyan paleoanthropologist and archaeologist Louis Leakey in 1962 and 1964. H. habilis or “handy man” was a proficient tool maker and was considered to have lived between 2.8 to 1.4 million years ago. The species had a larger brain than A. afarensis.
The next major species to emerge was Homo erectus, or upright man, which was originally discovered in Java in 1886 and existed from 1.89 million years ago to 143,000 years ago. H. erectus had a body structure very similar to modern humans and was known to be able to run considerable distances. The species was associated with the significant invention of hand axes and was the first to migrate out of Africa.
Our species, Homo sapiens, or intelligent man, was thought to have evolved 300,000 years ago. Numerous other Homo species have been discovered, but it is not always straightforward to determine their exact relationships. The ability of scientists to extract DNA from relatively recent fossils has enabled a better estimation of the complex genetic connections.
Neanderthals are considered our closest relative and were known to have existed 400,000 to 40,000 years ago. They had a much stockier body than H. sapiens but a similar sized brain. They had a very sophisticated tool kit and had mastered the use of fire. Some scientists consider them a subspecies of modern humans and have found evidence of interbreeding.
A limited number of bone fragments discovered in Siberia in 2010 have been called Denisovans. A finger bone indicated a robust body structure similar to Neanderthals. Mitochondrial DNA analysis has shown a close similarity to Neanderthals and modern humans. Part of the Denisovan genome is shared with modern humans in South East Asia and Australian Aborigines.
The period that the latest discovery, H. luzonensis, is known to have existed is a complex one for human evolution. Recent discoveries have shown that several hominin species existed contemporaneously, including modern humans, Neanderthals, Denisovans and H. floresiensis.
A recent study published in Nature in February, “Mosaic dental morphology in a terminal Pleistocene hominin from Dushan Cave” in southern China reported the discovery of atypical H. sapiens fossils that were 15,000 years old with primitive characteristics similar to H. luzonensis and H. floresiensis.
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