June 1, 2017

Recent studies show that Homo naledi, an intriguing species of prehistoric humans, may have lived far more recently than previously believed. Paleoanthropologists (scientists who study human evolution) say that H. naledi, a primitive hominin (human ancestor) known from a collection of fossils discovered at the Rising Star cave system in South Africa, may have lived at the same time and in the same region as more advanced prehistoric humans. Other new evidence shows that H. naledi may have had remarkably modern cultural practices that are seen among living people today, including funeral customs.

This nearly complete adult Homo naledi skull was found in the Rising Star cave system in South Africa. Credit: © John Hawks, Wits University

Between 2013 and 2017, an international team of excavators recovered more than 1,500 fossilized bones from the Rising Star cave site about 30 miles (48 kilometers) northwest of Johannesburg. The fossils were discovered in two deep cave chambers called Dinaledi and Lesedi (meaning stars and light in the local Lesotho language). Scientists quickly recognized the fossils as belonging to a previously unknown hominin that they named H. naledi. The anatomy of H. naledi shows a brain case less than half the size of that of modern people. The anatomy of the hands and shoulders suggests H. naledi was adept at climbing trees. These primitive characteristics suggest H. naledi lived perhaps 2 million years ago, when the first humanlike creatures appeared in Africa.

The fossilized remains of this Homo naledi skeleton suggest a stature of about 5 feet tall (150 centimeters). Credit: © John Hawks, Wits University

This May, researchers led by geoscientist Paul Dirks of James Cook University in Australia determined the age of the Rising Star cave fossils and their surrounding sediments using a combination of dating techniques. The fossils and sediments were determined to be between about 335,00 and 236,000 years old. These dates are much more recent than most scientists thought possible for such a primitive-appearing hominin.

The scientists who examined the fossils also suggest that the hominins called H. naledi may have intentionally placed their dead at the site—a remarkable behavior not seen among most ancient human ancestors. They point out that the Dinaledi and Lesedi chambers are deep underground and cannot be easily reached from the surface. By studying the sediments in the chambers, scientists could see that the bones had not been washed into the site by floodwaters.

Through studies of the fossil record, scientists know that other hominins lived in Africa and elsewhere at the same time as H. naledi. These archaic humans include Homo heidelbergensis, who were physically different from modern people, yet far more advanced than H. naledi, with larger brains and sophisticated stone tool cultures. However, evidence of intentional burial or other funeral customs is completely unknown from the fossil record of these early hominins.

Scientists contend the discovery of more H. naledi bones in another difficult-to-access part of the cave system supports their hypothesis that these hominins deliberately placed their dead in these locales. Such mortuary behavior was thought to be exclusive to larger-brained Homo sapiens.

In 2017, more H. naledi fossils were excavated from the recently found Lesedi chamber of the Rising Star cave system. The Lesedi chamber has no direct connection to the Dinaledi chamber. The fossil remains of at least three individuals were recovered from Lesedi. The remains include the well-preserved skeleton of a child and an adult male with a nearly complete skull.

Scientists are puzzled by how the remains came to be in the Lesedi part of the cave. The chamber contains almost no other ancient remains. Many of the hominin fossils were discovered undamaged with no evidence of being bitten or chewed by predators. Here too there was no evidence that the bones were washed into the site by floodwaters. If the remains were not intentionally placed there, as the evidence suggests, another possibility is that the hominins somehow became trapped in the cave and died together. If the hominins known as H. naledi did indeed practice funeral customs, they would be the earliest known hominins to do so.

September 16, 2015

Illustration of the fossils, sediments, and flowstones within the Dinaledi Chamber of the Rising Star cave system.
Credit: Paul H. G. M. Dirks et al (licensed under )

Last week, scientists from the University of the Witwatersrand in South Africa reported on a new find. Lee Berger, an American paleoanthropologist (expert on human evolution), and his colleagues unveiled a huge collection of fossils from the Rising Star cave site, about 30 miles (50 kilometers) northwest of Johannesburg. The fossils represent a previously unknown prehistoric human species. The scientists have named this new species Homo naledi. The Latin word Homo means human being, while naledi means star in the Sotho language of South Africa.

The Rising Star fossil site was first discovered in 2013 when spelunkers (people who explore and map caves) noticed an unusual number of fossilized bones in a huge cave complex they were exploring. The spelunkers alerted Berger, who hired a number of them to help recover the fossils from the narrow tunnels of the large underground caverns. Berger hired spelunkers of small stature to recover the fossils because the scientists could not fit through the narrow passage into the cave—only 7.1 inches (18 centimeters) wide. Over the following months, the team collected 1,550 fossils, representing partial remains of at least 15 individuals—the single largest collection of hominins ever found at a site in Africa. (In scientific classification, hominins are the group that includes human beings and early humanlike ancestors.)

Berger and his colleagues classified the fossils as a new hominin species based on the unusual anatomy of the fossils, which show an odd mix of primitive and modern features. The skull of Homo naledi is rounded like a human skull, yet small, with a brain only about one-third the size of a modern human brain. The front teeth are small, like humans, but the molars (back chewing teeth) are quite large. They had a small, thin body, and the bones of the shoulder and hands suggest they were adept at climbing trees. Yet the legs and feet show they were able to walk upright and possibly to make and use stone tools, as could the earliest humans.

The scientists have not been able to determine the precise age of the fossils, so it is difficult to determine exactly where Homo naledi fits on the human family tree. Most paleoanthropologists think that the first people evolved from an Australopithecus ancestor. Homo naledi may be a very close relative to such an ancestor. The scientists are also puzzled by the Rising Star site itself, which preserves almost no fossils of other kinds of animals. This may indicate the hominins at the site became trapped in an unusual event, such as a flood, and died together. However, Berger suggests that Homo naledi may have intentionally buried their dead at the site, a uniquely human behavior. Such behavior is virtually unknown among other species of early human ancestors.

Other World Book article

• Funeral customs