Interspecies competition in ancient humans saw an evolutionary trend that is the complete opposite of almost all other vertebrates, according to a new study.
For years, scientists assumed the main driver of the rise and fall of hominin species (which includes humans and our direct ancestors) was climate change. It is known, however, that interspecies competition is also at play as it is in most vertebrates.
New research published in Nature Ecology & Evolution examines the rate at which new species of hominin emerged over 5 million years. This speciation in our lineage, they found, is unlike almost anything else.
“We have been ignoring the way competition between species has shaped our own evolutionary tree,” says lead author Dr Laura van Holstein from the University of Cambridge, UK. “The effect of climate on hominin species is only part of the story.”
In most vertebrates, species evolve to fill ecological “niches.”
“The pattern we see across many early hominins is similar to all other mammals,” van Holstein says. “Speciation rates increase and then flatline, at which point extinction rates start to increase. This suggests that interspecies competition was a major evolutionary factor.”
But van Holstein describes as “bizarre” the evolution of the group Homo which includes modern humans and emerged about 2 million years ago with Homo habilis.
The trend of speciation was completely reversed.