Modern humans enjoy free rein of the Earth at present, but a newly discovered human species in the Philippines make it evident that this wasn't the case for ancient hominins.

Instead, several human species likely lived alongside each other before the family tree whittled down to just modern humans.

In a study published in the journal Nature, scientists share details of their landmark discovery in the Philippines: a new human species called Homo luzonensis, named after the island of Luzon where they were unearthed.

A Strange Mix Of Traits

Dated to 67,000 years ago, these remains of two adults and one juvenile excavated from Callao Cave in Luzon are the oldest hominin evidence ever found in the Philippine archipelago. More interestingly, the H. luzonensis feature an odd mosaic of ancient and modern traits that set them apart from other human species.

The study authors analyzed all the fossils collected, which include foot and hand bones, teeth, and a partial femur.

Their presence and their odd mix of traits throw the entire homonin family tree in intriguing disarray. For instance, the various molar and premolar teeth presented similarities to Homo sapiens, Homo erectus in Asia, Homo floresiensis, and even the Paranthropus. The toe bone is curved and monkey-like, much more similar to the Australopithecus afarensis who lived millions of years ago.

"This phalanx strongly resembles those of Australopithecus, known only in Africa and at much older periods (about 2 to 3 million years ago)," Florent Détroit, study author and archaeologist from the Muséum National d'Histoire Naturelle, told Science Alert.

Several Human Species Roamed The Earth In The Past

The age of Philippines' H. luzonensis means that they roamed the Earth at the same time as other hominins such as the H. sapiens, Neanderthals, Denisovans, and Homo floresiensis.

For a long time, many experts believed that H. erectus left Africa around 1.5 million to 2 million years ago, according to a report from Nature. Other hominins supposedly stayed put in Africa where these species eventually faced extinction. Some of these species include the Homo habilis, Paranthropus, and Australopithecus.

Many discoveries in previous years challenge this early and orderly theory about the origin of human evolution. One such discovery is the H. floresiensis, the "hobbit" species found in the Flores Island of Indonesia in 2004.

Finding a new human species in the Philippines that shares traits with long-extinct hominins from millions of years ago further supports the growing conviction that H. erectus isn't the only hominin species that traveled out of Africa.

Like the H. floresiensis, the H. luzonensis lived on an island that can only be reached with a sea crossing. It's possible that both species evolved from H. erectus populations who lived and evolved in these isolated islands for a long time.

"[A] few thousands of years back in time, H. sapiens was definitely not alone on Earth," Détroit stressed.

Rainer Grün, study author and archaeogeochemist from Griffith University, agreed in an interview with Science Alert.

"Human evolution is far more complex [than we realised] and it was normal in the past to have several human species living side by side. In contrast to today where we are the only species left," Grün explained.

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