The temporal lobes of Homo erectus were proportionally smaller than in H. sapiens

The temporal lobes of Homo erectus were proportionally smaller than in H. sapiens

The CENIEH has contributed to a paleoneurological study published in the journal Quaternary International, on the brain of Homo erectus, which analyzes its temporal lobes and compares these with other species like H. ergaster and H. sapiens
temporal lobes erectus sapiens ergaster
Pearson at al.

Emiliano Bruner, a paleoneurologist at the Centro Nacional de Investigación sobre la Evolución Humana (CENIEH), has participated in a study published in the journal Quaternary International, on the anatomy of the temporal lobes in the brain of Homo erectus, which establishes that they were proportionally smaller than in modern humans.

In H. sapiens, the temporal lobes are relatively more highly developed than in other primates, although little is known about their anatomy in extinct human species, because they are housed in a very delicate region of the cranium known as the middle cranial fossa, which is often not conserved in fossil individuals.

An earlier study by the same team had shown that the size of the middle cranial fossa can be used to deduce the volume of the temporal lobes. In this new study, three anatomical diameters were analyzed in fossils of H. erectus and H. ergaster, and compared with the corresponding measurements for 51 modern humans. The results suggest that both fossil species had temporal lobes proportionally smaller than in humans today.

Moreover, “The Asiatic individuals, namely Homo erectus, had larger temporal lobes than in the African ones, Homo ergaster, although the scanty fossil record does not allow us to tell whether this is due to chance or a paleoneurological difference between the two species”, says Bruner.

As the temporal lobe is a brain region involved in the integration of many cognitive functions, such as memory, the emotions, hearing, social relations and language, any change in their sizes or proportions is of transcendent importance, as this could reveal variations in the development of their neurons or their connections, and therefore in the cognitive functions associated to this region of the cerebral cortex.

This study has been conducted by Alannah Pearson, a doctoral student of Emiliano Bruner at the Australian National University in Canberra (Australia), in collaboration with Professor David Polly, of Indiana University (USA).

 

Full bibliographic information

Pearson, A., Polly, P. D., & Bruner, E. (2020). Temporal lobe evolution in Javanese Homo erectus and African Homo ergaster: inferences from the cranial base. Quaternary International (0). doi: 10.1016/j.quaint.2020.07.048.

 

Press release from CENIEH


Holy Pleistocene Batman, the answer's in the cave

Holy Pleistocene Batman, the answer's in the cave

Let's say you wanted to solve a 20,000-year-old mystery, where would you start?

biodiversity Borneo Sumatra Java Sundaland Sunda Sahul
The Sahul Shelf and the Sunda Shelf today. The area in between is called "Wallacea". Picture by Maximilian Dörrbecker (Chumwa) - self made, using this map for the background; CC BY-SA 3.0

Let's say you wanted to solve a 20,000-year-old mystery, where would you start? Perhaps archaeology and geology come to mind. Or, you could sift through a 3-metre pile of bat faeces.

Researchers from James Cook University in Cairns, Australia, chose the bat poo in their quest to answer to a long-standing question: why is there some much biodiversity on the islands of Sumatra, Borneo and Java, when not so long ago (geologically speaking) they were all part of one vast continent?

One theory has been that the former continent (Sundaland) was dissected by a savanna corridor. "That might explain why Sumatra and Borneo each have their own species of orang-utan, even though they were linked by land for millions of years," Dr Chris Wurster said. "The corridor would have divided the two separate rainforest refuges, as the sea does now."

The corridor theory has been boosted by millions of insect-eating bats, which have gathered evidence about the landscape over millennia and deposited it in layers in their caves.

"Bat poo is highly informative, and especially so in the tropics, where the climate can make some of the more traditional modes of investigation less available," Dr Wurster said.

A three-metre pile of bat faeces at Saleh Cave in Borneo gave the researchers a 40,000-year-old record composed of insect skeletons.

"We can't tell what insects the bats were eating throughout that time, because they're in tiny fragments, but we can read the chemistry," Dr Wurster said.

"Eating insects that have been feeding on tropical grasses results in faeces with a characteristic chemical imprint. It's quite different from the result you'd get from eating insects that fed on tropical trees."

According to the bat record the landscape around Saleh Cave (now featuring lush rainforest) was once dominated by tropical grasses.

"Combined with other cave studies in the region, this leads us to support the corridor theory, and also gives us some confidence as to the extent of the corridor," Dr Wurster said.

The corridor could also shed light on human pre-history.

"A savanna corridor, which would be much more easily traversed than rainforest, might help to explain how people moved relatively quickly through this region and on to Australia and New Guinea."

'Savanna in equatorial Borneo during the late Pleistocene' is published in the latest edition of Scientific Reports.

Dr Chris Wurster is a Senior Research Associate at James Cook University, specialising in stable isotope geochemistry.

 

 

Press release from the James Cook University