The chart above illustrates how human evolution hasn’t been a simple, linear path, but rather separates into branches and bush-like groups. To repeat, it’s more of a messy zigzag that has occurred over 7 million years. Scientists have uncovered much about our ancient ancestors, about who we are and how we got here. Yet, this isn’t the pretty, static picture that is portrayed by the Genesis version of creation. It is fluid, complex and subject to revision with the next great discovery.
Nevertheless, much is known and has been proven with an extraordinary treasure trove of fossils, DNA analysis and massive genome projects, radiometric dating, coupled with advances in biogeography, molecular taxonomy, and other related disciplines. Over 20 types of hominins have been identified as separate species. Our ancient relatives were bipedal primates who slept in trees to avoid predators but also walked and ran on two legs. Evolution freed their hands from knuckle-walking and eventually started increasing brain size; this allowed our hominin ancestors to make tools and make fire.
Our overview of human evolution has already included Homo heidelbergensis, a species that likely evolved from Homo erectus and lived from about 600,000 to 200,000 years ago; they became the parent species of both Neanderthals and Humans. Homo heidelbergensis traveled outside of Africa to the cold climates of Europe and also to the Far East. Our parent species was also the first to make shelters and hunt big game with wooden spears.
According to the Smithsonian Institution’s “Human Origins” project, the greatest climate fluctuations of the Pleistocene began about 800,000 years ago. This is also the period in which our ancestors developed larger and larger brains.
Once we trace our evolution to within 300,000 years ago, we discover that at least six species of our genus Homo co-existed on this planet at the same time. Recent fossil discoveries have revealed two previously unknown species of Homo that lived within this time frame.
The fossil remains of Homo naledi were discovered in 2013 deep inside of The Rising Star cave system in Southern Africa near Johannesburg. Paleoanthropologist Lee Berger and his team discovered over 1,500 fossils from 15 specimens. Some of the chamber openings were so tight that the team used small women to navigate them to the discovery areas. In 2017 they published the results of the radiometric dating of Homo naledi fossils from 335,000 to 236,000 years old. Scientists were shocked by the young age of this species that possessed primitive traits going back 2 million years. Human-ape hybrids weren’t supposed to have survived this long. Yet the fossil records of this diminutive species (4’8” tall, 88 to 120 lbs.) are undeniable.
As Professor Chris Stringer explained, “Some of Homo naledi’s features, such as its hands, wrists, and feet, are very similar to those of modern humans and Neanderthals.
“Other characteristics are much more primitive. The species’ small brain and the shape of its upper body are more similar to the pre-human australopithecines and the very early human species Homo habilis.” (Berger et al., 2015)
Perhaps Homo naledi was an outlier who co-existed in time but not in place with the other species of Homo that lived in Africa. As usual with new discoveries, many questions linger over this species that logically shouldn’t exist. Messy, very messy!
(to be continued in next post)