In the Cave of Callao, located on the Philippine island of Luzon, a new human species has been discovered: Homo luzonensis. The study of its fossils, from 50,000 to 67,000 years old, reveals a unique mixture of characteristics that differentiates it from other species..
A multidisciplinary international team, codirected by Florent Détroit, titular professor of the Museum of Natural History of Paris (France), has analyzed several bones of the foot and of the hand, a partial femur and teeth of ancient hominids found in the Cave of Callao, In the Philippines.
Some of these fossils provide sufficient evidence that a new species of hominids, which they have called Homo Luzonensis, lived on the island of Luzon 50,000 years ago, during the Late Pleistocene period. The first fossil was discovered during the excavation of 2007 in the campaign organized by the scientist Armand Mijares, from the University of the Philippines. Later, in 2011 and 2015, we found all the fossils published today by Nature magazine.
“What makes it a new species is the combination of all the features we have described of H. Luzonensis together. Each separate one can be found in one or more hominid species. This also indicates that it has more affinities with species of the genus Homo, than with other genera of hominin such as Australopithecus or Paranthropus. If the entire package is taken, no other species of the genus Homo is similar “, declares a Sync Détroit.
For the investigator, the most surprising and interesting element of those who have found is the phalanx of the CCH4 foot, due to its very unusual shape and morphology for a ‘ recent ‘ species of the genus Homo. “I Remember the day we found him, during the excavation of 2011, I had the discussion with a Filipino colleague who is a bioanthropologist specializing in H. sapiens, because he could not accept that it was a phalanx of the foot. It Is One of the most interesting elements of H. Luzonensis because It shows surprisingly primitive features, such as Australopithecus, “he adds.
The teeth also present an astonishing combination of primitive and modern morphological features. “They Are well documented in the hominid fossils register and are well known for their taxonomic and phylogenetic value. The teeth of the luzonensis are extremely important, “he continues.
Homo Luzonensis is described from a set of fossil bones and teeth that belonged to at least three individuals. Two of these fossils are between 50,000 and 67,000 years old according to the analysis of uranium series. They Are The first known human remains in the Philippines, which precede the first of Homo sapiens, from 30,000 to 40,000 years, discovered on the island of Palawan, in the south-west of the archipelago.
With Regard to the controversy that always involves this type of studies on human evolution and new species, the expert replies: “Of course, some colleagues will question the legitimacy of describing a new species based on a fairly small set of fossils , but the question of what is a species is a very debated issue that will not be resolved (nor will it become more complicated) with a discussion about whether it was a good or a bad idea to describe H. luzonensis. “
Détroit estimates that if his scientific colleagues can prove that they are wrong because fossils could enter one of the species of hominids already known, “we will simply group and forget, but in the meantime, I am convinced that it is the way in which We have to do this to improve our knowledge and understanding of the evolutionary history of the hominids. “
The appearance of Homo luzonensis
One of the questions that always arises when one speaks of the discovery of a new species is about its appearance and behavior. However, because of the scarce elements with which they count, scientists are wary of estimating, for example, the body size of H. Luzonensis.
The strongest arguments indicate that he was probably a small-bodied hominid, the size of the denture and the metatarsal (published in 2010). The teeth are very small – more than those of Homo floresiensis – and we know that in primates there is a strong correlation between the size of the teeth and the body size, but, of course, it is not a strict rule and there are several exceptions. ” According to researchers, it should not have the image of H. Floresiensis as a model for its physical appearance, since it was also shown that the length of the metatarsal was within the range of the small body or ethnic groups called Negritos of the Philippines.
They Also believe that the way they walked might be different. The article mentions several characteristics of the bones of the foot that are very similar to Australopithecus and that are generally interpreted as evidence of a mixed locomotive behavior, bipedal on the ground and still climbing trees.
“We Do Not suggest that H. Luzonensis has returned to the trees for all we know about the evolution of the foot in the genus Homo. In our opinion, the effects of insular endemism could explain the recurrence of such primitive characteristics. But It is a very interesting question to address: whether they were strictly bipeds like all members of our gender or whether these primitive characteristics influenced or changed their biped gait. It is Still too early to answer, “says Détroit.
On the other hand, they are also not sure whether these individuals lived in the cave or not. “During The excavation we do not identify the current ‘ living flats ‘ in this old layer containing hominid fossils. Some H. Luzonensis Puodrían have carried out activities, for example of cutting, just from or to the entrance of the cave and the bones and teeth could have been displaced in later. There Are still several hypotheses, says the scientist.
Mixture of very modern traits and other very archaic
The analyses performed on fossils, using 3D images and geometric morphometry, show that H. Luzonensis has very primitive elements, similar to Australopithecus and others that are very modern, close to our own species Homo Sapiens.
The bicuspids of The same individual have between two and three roots, while in H. Sapiens there is usually a root and sometimes two. By this characteristic and by the morphology of the enamel, they are more similar to those of the Australopithecus and species like Homo habilis and Homo erectus. In contrast, the molars are very small and have a very simple morphology, such as those of H. sapiens. There is no individual with these characteristics combined in any of the species known today.
Likewise, the bones of the feet have in the proximal phalanx a very marked curvature and very developed insertions for the muscles involved in the flexion of the foot. These characteristics are also not typical of H. sapiens but they are very similar to the phalanx of Australopithecus, known only in Africa and in much older periods (between 2 and 3 million years ago).
The H. Luzonensis were alone
In Addition to the recovered bones and teeth, the same layer found a faunistic ensemble dominated by the Philippine Brown deer, with fewer endemic warty pigs and small extinct bovines, similar to the dwarf buffalo of Mindoro (Bubalus Mindorensis) Current.
“As far as we know, H. Luzonensis was the only hominin present in Luzon at the time. The first known H. Sapiens in the Philippines are the fossils discovered in the cave of Tabon on the island of Palawan, “concludes the scientist.
The relevance of Luzon in the evolution of the genus Homo
Luzon is a large island that has never been accessed through a land bridge throughout the Quaternary. Its fauna and Flora are known for its high rate of endemism. This explains the decrease in their genetic diversity and is visible in the form of species that often differ much from their sister species that have remained on the continent.
The oldest traces that indicate the presence of hominids on the island date back to about 700,000 years ago. Homo Luzonensis, whose fossil remains are about 600,000 years younger, are probably a species that evolved under the influence of the endemism of the islands, in parallel with the evolutionary history of Homo floresiensis on the island of Flores, Indonesia. “Southeast Asia, especially the islands, is a fantastic place to study human evolution, prehistory, paleoanthropology,” says Détroit.
The origin and modalities of the arrival of this new species to the island of Luzon remain largely mysterious at the moment, but this discovery underscores the diversity, richness and complexity of past migrations and the evolutionary history of Hominids on the island of Southeast Asia.
“The main hypothesis is that few individuals crossed the sea successfully and settled on the island of Luzon. Then, isolated from the rest of the initial population that remained on the continent. They Probably suffered the effects of what is called Insular endemism, which is generally expressed in rapid changes in morphology and gives new species that differ significantly from the individuals of the continent, “explains the researcher.
Maritime Navigation is also a burning question, but very difficult for scientists to answer. “There Are two main assumptions: purely by accident and intentional navigation. For the second, we can imagine the hominids practicing something very different from what we call navigation now. Homo erectus, for example, was not large enough to cross the sea on purpose, but the fact is that we now have more evidence that they were successfully established on several islands in the remote past of Southeast Asia, so it was probably not as Accidental! “exclaims Détroit.