No, this is not the title of a new science fiction novel. This is science reality!
Recently, a team of paleoanthropologists led by Dr. Lee Berger discovered the fossil remains of a new human ancestor in South Africa. The new fossils, called Homo naledi, were named after the Rising Star Cave in Johannesburg, in which they were found. Naledi means “star” in the local Sesotho language. Homo naledi is regarded by many scientists to be a whole new species and an extremely important find in the study of human evolution, possibly as important and influential as the famous Lucy fossil discovered in 1974.
A photo of Dr. Berger inside the Rising Star Cave.
As is the case with many scientific discoveries, the fossils were found by accident! Two years ago, a pair of spelunkers made their way through the Rising Star Cave when they discovered the massive deposit of human-like remains. They reported their find to Dr. Berger, who had been conducting research at the University of Witwatersrand in Johannesburg since the 1990’s. It is truly amazing that they found these fossils because the cavers had to go through an extremely skinny and dangerous passage called “Superman’s Crawl”, which is only about 8 1/2 inches wide! For this reason, the entire team of six anthropologists who discovered the remains were women. Women tend to be smaller than men and thus can more easily make it through “Superman’s Crawl”. They have been nicknamed “underground astronauts”!
The six “underground astronauts”, who risked their lives to make this discovery!
There are two very striking traits of Homo naledi that have gotten anthropologists so interested in this discovery. First, the fossil is a very strange synthesis of traits from Australopithecenes (early human ancestors who walked on two feet) and hominins (same genus as modern humans; big brains and tool makers). For example, the brain of Homo naledi, based on skull size, is only about the size of an orange. However, the most complete skeleton found from the fossil site measures about 5 feet tall, and that individual probably weighed about 100 pounds. This is much bigger than the Lucy fossil, an Australopithecene, who measures about 3 1/2 feet tall and only weighed about 60-65 pounds. This suggests to some anthropologists that Homo naledi may have been a species right in between the two groups from an evolutionary perspective.
A table demonstrating the Homo (hominin) and Australopithecene features of Homo naledi.
The second intriguing charateristic is behavioral, not physical. The fossils found in Rising Star Cave, representing 15 different individuals ranging from infancy to the elderly, appear to have been deliberately placed there. In other words, Homo naledi may have buried their dead. This is a trait previously thought to only be exhibited by modern humans! The oldest known human burial is only 100,000 years old, and geologists estimate the cave to be about 3 million years old!
Rising Star Cave: a prehistoric, prehuman burial site?
Scientific breakthroughs are often met with healthy skepticism, and Homo naledi is no different. Some scientists simply do not agree with the amount of hype and importance this fossil have been given. Others are wary of assigning new fossils as new species too quickly. Often, fossil evidence is scant, with only a piece of skull or femur discovered in one site, so it can be hard to determine species from the fossil record alone. Several factors other than speciation can account for physical difference between fossils, such as biological sex, environmental factors, or even just two very different individuals from the same species. The process of naming extinct fossils can seem extremely arbitrary, and there may be some bias from the discover(s) involved in the process (who doesn’t want to discover a new species?)
A reconstruction of a Homo naledi skull and face; does it really represent a new species?
The sheer amount of fossil evidence discovered does provide an incredible wealth of data to determine whether Homo naledi is a new species or not. Admittedly, anthropologists are not sure of the age of the Homo naledi fossils becasue they were found in varying ages of soil. It is important to know the chronological context of any fossil so that its place and significance in human evolution can be properly determined.
The entire collection of Homo naledi fossils found; over 1500 fragments from 15 different individuals.
Whatever its true significance may be, there is no denying that Homo naledi makes us wonder what it means to be human. If not a new species, it sure is interesting!
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