Competition among species had a significant impact on the growth and decline of hominins, resulting in an unusual evolutionary pattern for the Homo lineage, as indicated by a recent University of Cambridge study that updates the timelines of many of our early ancestors. Conventionally, climate has been considered accountable for the emergenceThe emergence and disappearance of hominin species is a well-known phenomenon in vertebrates. However, research has now shown that competition played a crucial role in the “speciation” process over a five million year period of hominin evolution. This study, published in Nature Ecology & Evolution, indicates that the species formation pattern in our own lineage was quite unique. Dr Laura van Holstein, the lead author, stated that the impact of interspecies competition on our evolutionary tree has been overlooked.mbridge biological anthropologist from Clare College, van Holstein, emphasized that the impact of climate on hominin species is just one aspect of the overall picture. He pointed out that in other vertebrates, species develop to occupy specific ecological “niches.” An example of this is seen in Darwin’s finches, where some evolved large beaks for cracking nuts, while others evolved small beaks for feeding on certain insects. Once a niche is filled with a species, competition arises, preventing the emergence of new species and leading to extinctions.
Van Holstein utilized Bayesian modeling and phylogenetic analyses to demonstrate that, like other vertebrates, most hominin species emerged when competition for resources or space was minimal. This suggests that competition played a significant role in the evolution and development of hominin species.
“The trend we observe in many early hominins is similar to that of other mammals. Rates of speciation increase and then level off, at which point rates of extinction begin to rise. This indicates that competition between different species played a significant role in evolution.”
However, when van Holstein examined our own genus, Homo, the results were “surprising.”
For the Homo lineage that led to modern humans, evolutionary patterns indicate that competition between species actually led to the emergence of even more new species — a complete reversal of the pattern seen in nearly all other vertebrates.
“The higher the number of different Homo species, the greater the rate of speciation. So when those ecological niches became filled, something drove the emergence of even more species. This is nearly unprecedented in the field of evolutionary science.”
The only similar comparison she could find was in beetle species that inhabit islands, where contained ecosystems can lead to unique evolutionary patterns.
“The evolutionary patterns observed across Homo species that directly led to modern humans resemble those of island-dwelling beetles more than other primates, or even any other mammals.”
In recent decades, several new hominin species have been discovered.The hominin fossil record is home to a variety of species, ranging from Australopithecus sediba to Homo floresiensis. Van Holstein has developed a new database that documents “occurrences” in this fossil record, tallying up to approximately 385 instances of a species being found and dated. Fossil records, however, may not always accurately reflect the lifespan of a species. Van Holstein points out that the earliest fossil found does not necessarily represent the earliest members of a species. This is due to various factors such as geology and climate conditions, which can affect the fossilization process. With research efforts primarily focused in specific regions of the world, there is a possibility of misinterpretation.
Van Holstein used data modelling to tackle this issue, taking into account the likely population size of each species at the beginning and end of their existence, as well as the impact of environmental factors on the fossilization process. As a result, new start and end dates were generated for a total of 17 known hominin species.
Her analysis revealed that some species previously believed to have evolved through anagenesis, where one species gradually transforms into another without a split in lineage, may actually have undergone budding. This occurs when a new species branches off from an existing one.
As a result of this discovery, it is now believed that there are several more hominin species than previously assumed.were living together and potentially competing.
Early hominin species like Paranthropus likely evolved physiologically to expand their niche, for instance by adapting teeth to take advantage of new types of food. However, the reason for the very different pattern in our genus Homo may have been technology.
“Adopting stone tools or fire, or using intensive hunting techniques, are highly adaptable behaviors. A species that can utilize them can quickly create new niches, without having to survive long periods of time while evolving new body plans,” van Holstein explained.
She suggests that the ability to use these technologies were what allowed certain species to thrive.The rapid advancement of technology and the ability of Homo species to adapt to various ecological niches may have contributed to the increase in the number of Homo species identified in the latest study. This adaptability also led to the emergence of Homo sapiens as the ultimate generalists, capable of thriving in almost any ecological niche. The competition with Homo sapiens, a highly flexible generalist, may have been a factor in the extinction of other Homo species. According to van Holstein, these findings highlight the important role that competition played in human evolution, which has traditionally been overlooked.ps most notably, within our own genus, it played a role unlike any other vertebrate lineage known to date.”
Notes: *For instance, the hominin species Australopithecus afarensis was thought to have evolved through anagenesis from Australopithecus anamensis. However, the new data modeling suggests they coexisted for approximately half a million years.