What Drove Homo Erectus Out of Africa?

A vast expanse of thistles and dry grasses stretches out into the distance on a hot summer day at Ubeidiya in northern Israel. The mountains of Jordan can be seen in the distance. Nearby are cultivated olive groves as well as a date palm plantation.
Ubeidiya is located south of the Sea of Galilee and can be reached by a dirt road. There are no signs to indicate its archaeological treasures. Ubeidiya's panorama would have been dramatically different 1.5 million years ago, according to Omry Barzilai of the Israel Antiquities Authority as he walks through hillside brambles. He says that you would have seen a large lake stretching all the way to Jordanian hills.

Hippopotami would have enjoyed aquatic plants. The landscape was densely wooded with wild oak, olive and pistachio trees. One might also have seen some modern human relatives on the lakeshore. They were a group of Homo Erectus who used sharpened stone handaxes to remove the carcass of a deer, or a hippo that had been killed by a saber toothed tiger.

Ubeidiya was one of the first sites that H. erectus settled on his journey out of Africa. Kibbutz Afikim, a local farming group discovered the ancient site in 1959 after it was named after a nearby Palestinian Arab village, may be key to understanding how H. erectus moved from its origin.

It is not clear what pushed or pulledH. It is still a controversial issue to determine what drove the erectus out Africa.

Did it come down to innate adaptability such as curiosity, social learning, social learning, or technological acuity. Was it the rapid climate change or expansion of grasslands that sent them on their way? Or was it a combination of all these factors?

There are many questions about resilience and innovation at stake. Miriam Belmaker, a paleoanthropologist at the University of Tulsa, Oklahoma, states that we must change the question to ask not only where, but also what and when, but why it was successful.

H. erectus is a fascinating species. It was discovered in fossil records around 2 million years ago. H. erectus is taller than any of its predecessors and has shorter arms.

They expanded over the course of 1.75 million years into Western Asia, then into Eastern Asia including what is now China and Indonesia. Andy Herries, a paleoanthropologist at La Trobe University, Melbourne, Australia, believes that H. erectus (which means upright man) was also the first runner.

Herries claims that Homo erectus was one of the most successful human races to ever live. It appears to have evolved around 2 million years ago. If the latest dates from Indonesia are correct Herries believes that Homo erectus is one of the most successful human species to ever live.

H. erectus was also a first homininmeaning that he belonged to our ancestral human line. He made teardrop-shaped, two-sided stone hand axes known as Acheulean Tools, which are the oldest of their kind, and date back to 1.7 million years. Most scholars believe that H.erectus evolved in Eastern Africa because of the abundance of fossils and tools found there. But a 2.04-million-year-old cranium, found by Herries in South Africa, indicates that these hominins were on the move 2 million years ago. H. erectus migrations from Africa to Africa are amazing in their scope and eventually allowed the species to live across half of the globe.

H. erectus crossed the Levantine Corridor on their journey from Africa to Europe, Asia and Africa. This narrow strip of land between the Mediterranean Sea and the desert to its east includes the present-day countries of Syria, Lebanon and Israel as well as Palestine, Palestine and Jordan. H. erectus visited the Ubeidiya site between 1.2 million and 1.6million years ago. It was a stop along his route through Levant.

Scholars subscribed to Savannahstan hypothesis for many years to explain hominin migrations from Africa. This idea states that H. erectus dispersed from East Africa around 2 million years ago, when climate change caused the expansion of East African Savanna into the Southern Levant.

H. erectus probably stayed close to water sources, rivers and lakes on their long journey. This is according to Bienvenido Martnez Navarro, a paleontologist at the Institut Catal de Paleoecologia Humana i Evoluci Social, Tarragona. They likely ate the meat of dead animals as scavengers. The original Savannahstan hypothesis states that these hominins are so adaptable to open grasslands and occasional patches of woods, and as the climate changed, they followed new savannas from Africa.

However, the discovery at Ubeidiya has complicated the idea that H. erectus was passively following the spread of savanna. Belmaker points out that Ubeidiya was not a savanna. It was a forest, covered with trees, which her work helped to establish.

The evidence for Belmakers' position is supported by the hundreds of thousands of fossilized bones of animals excavated at Ubeidiya. These bones are mostly kept in drawers at National Natural History Collections of the Hebrew University of Jerusalem. They include the teeth and bones from rhinoceroses and hippopotamis, crocodiles and bears, as well as crocodiles and crocodiles. The 6-foot-wide horns, which measure 6 feet in width, of an extinct buffalo species are located at Jerusalem's Israel Museum. They can be found near the colorfully misnamed monstrous sheep Pelorovis Oldowayensis.

Belmaker explained that most hoofed mammals at Ubeidiya were Eurasian. This suggests that it was not an African savanna. Extinct horses, deer, and giraffes have wear patterns that suggest they ate soft leaves more typical of woodland vegetation than grassland.

Belmaker also compared the compositions of four Eurasian hominin sites and Ubeidiya's carnivore fossils from the Early Pleistocene (between about 2.6 million and 770,000 years ago). Two of the H.erectus sitesDmanisi, in Georgia, and Pirro Nord, in Italy, were inhabited by a variety of animals, including hyenas, dogs, and other species that prefer open, long-distance running environments. This suggests that these sites may have been shrub or grassland. Three other sites, Ubeidiya, Venta Micena and Akhalkalaki, in Georgia, had a wider range of ambush hunters than the ones at Dmanisi in Georgia. These animals, such as felines, rely more on trees so it is possible that these sites were forested.

H. erectus can thrive in multiple habitat types, according to Belmakers' findings. It was not restricted to savannas. She has a new theory for migration based on her findings: H. erectus was naturally adapted to different landscapes, even before other groups left Africa. This includes hunting antelope in open plains, and clearing forest patches.

Belmakers' hypothesis is supported by evidence from Eastern Africa that H. erectus was well equipped to thrive in all kinds of habitats. Isabelle Winder (zoologist at Bangor University, Wales) has found that the African Rift Valley where H. erectus was discovered would have been characterized by uneven or rough terrains rich in basins and caves that held water and sediments.

These spaces provided hominins with places to hide from predators and forage. However, the difficulties associated with these habitats meant that individuals with adaptations that increase their survival in multiple habitats (e.g. feet that act like levers to help hominins climb over boulders) would be most likely to survive and reproduce. H. erectus may have evolved more versatility over time.

Winder states that such complex terrain can also be found along coastlines and would have provided plausible routes out of Africa, which would have facilitated early Homo's expansion. These diverse landscapes featured hills, valleys and patches of forest, as well as water and diverse vegetation.

Belmaker also believes H. erectus adaptations may have been more than physical capabilities. She claims that H. erectus was unique in biological and social ways.

Belmaker refers to a skull that belonged to H. erectus' ancestor from the 1.77million-year-old Dmanisi Site in Georgia as support. The bones are likely to have been left behind by a man who had lost his teeth in the years before his death. Although there are many possible scenarios, Belmaker suggests that this hominin survived because others took care of him. They helped with the hard work involved in gathering, hunting and preparing root vegetables.

These ideas are a radical reimagining of the capabilities of ancient hominins. Belmaker concludes that Homo erectus wasn't a passive organism in its environment. It was not passive and went with the flowOh, more grassland. Ill move there, but an active participant in its own destiny. It is very possible that they choose to live in forests.

Others agree with H. erectus' ability to adapt to different environments.

According to Rick Potts (head of the Smithsonian Institutions Human Origins Program), evolution has seen a rise in different abilities to inhabit different environments. He says that this includes eating more foods and being able cognitively and socially to adapt to different situations.

He points out that H. erectus was present in tropical Southeast Asia and Indonesia around 1.4 million to 1.6million years ago. This is a sign that not only one habitat is being monitored.

Potts however believes that there was an immediate trigger that triggered adaptations: periods with highly variable climate.

Potts began to think about the possibility that climate variability could be a factor in major evolutionary changes since the 1980s. He believes that only those with certain traits can survive and thrive in times of sustained and rapid climate change. This will allow them to raise children who, in turn, can pass on the beneficial traits and shape human evolution.

Cognitive abilities, such as the ability to create sophisticated stone tools, could have enabled people to eat different foods in different environments. A trait such as curiosity could have encouraged hominins move to humider climes after the landscape dried.

Potts emphasizes that Homo erectus did not have a map. They didn't know that they were outside of Africa. They were simply going to the next valley to check out what was there. This would have lead to dispersal over generations.

Potts published a paper in 2015 in the Journal of Human Evolution. He looked at several species of hominins to see if there were signs that climate variability favors the development of beneficial traits. Together with anthropologist Tyler Faith, now at the University of Utah, the pair mapped periods of high and low climate variability for tropical Eastern Africa over the past 5 million years, specifically looking at once-every-100,000-year shifts in the Earths orbit that prompt more frequent switches between periods of drought and high rainfall. Faith and Potts found that high levels of climate variability were associated with important milestones such as the emergence and development of advanced stone technology, migration, brain growth, and bipedal australopithecines.

Numerous major milestones in hominin history, such as the dispersals H. erectus or H. sapiens, occurred during periods of high, prolonged climate variability. Potts said that the pattern was so obvious, it looks rigged.

What could climate variability have done to H. erectus's development? Peter de Menocal is a marine geologist and climate scientist. He has used layers of sediment from the East African coast to study climate changes over 1.9 million years. He notes that the 2 million year period [ago] marks one of the most important junctures of human evolution.

De Menocal claims that there were many adaptations, such as the slimmer bodies and longer legs, which gave H. erectus an increased ability to run or walk long distances. He says that more meat was available on the savanna, which could have helped to sustain their increased energy needs. The increase in brain function presumably resulted in a greater ability for planning, coordination, and communication.

The bifacial Acheulean Axes, which are much more advanced than the earlier hominin tools, is one important H. erectus innovation. It first appeared in the fossil record at Kokiselei in Kenya 1.76 million years ago. These tools may have been supported by cognitive and physical adaptations. This could also be related to extreme climatic changes. Rachel Lupien, a postdoctoral researcher scientist at Columbia University's Lamont-Doherty Earth Observatory, identified a shift in climate from arid to humid, rainy, using chemical signatures in plant waxes found in the Turkana Basin sediments. This coincides roughly with the advent of this technology.

Lupien said that Acheulean handaxes were better suited to rapid environmental changes. Lupien also says that they were more multipurpose tools, which allowed H. erectus thrive in many environments.

Lupien believes that H. erectus could have dispersed from Africa because of its natural adaptability and rapid climate changes. She emphasizes that climate variability is likely to have played a significant part. I've seen very large climate swings coincide with the most recent dates on these transitions. This coincidence is not random.

Some scholars still believe in a Savannahstan hypothesis variation, which presents savanna with a mixture of grassland as well as some woodland. Many people are still debating H.erectus's journeys out Africa. The question is not whether H.erectus was adaptable in different landscapes but what drove this flexibility.

Belmaker acknowledges that Potts hypothesis has nice correlations between climate changes and the emergence new adaptations. She says that each generation of H.erectus would have seen the climate as relatively constant after a long period of climate variability. She believes that climate change wouldn't have had a significant impact on the passing of traits from one generation into the next.

Belmaker also argues that many milestones that Potts considers to be related to climate change were not present at all. Stone tools can be traced back to 3.3 million years ago, long before H. erectus arrived on the scene.

Belmaker believes that adaptability is a part of the ancestral DNA of these hominins. She believes they were successful because they were socially connected and generalists.

Others, such as de Menocal, are convinced that our origin story is fundamentally linked to environmental changes. This is especially important as H. sapiens faces its own human-caused climate change.

We were smart. We were smart. Our history has been one of adapting to big changes. The bigger takeaway is that we must pay attention to threats.

This story originally appeared in Sapiens, an anthropology journal.

Josie Glausiusz, a science journalist from Israel, is the author of this article.