A new study has reinforced the claim that neanderthals and modern-day human must be classed as separate species.
Homo sapiens and neanderthals originate from the same ancestor but there is a long-standing debate amongst researchers as to what classifies as a species.
According to the report published by experts from London’s Natural History Museum and Institute of Philosophy KU Leuven in Belgium, there can be no doubt.
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According to Professor Chris Stringer and Dr Andra Meneganzin, these are two different species.
Despite limitations in the fossil record, they found that there is enough evidence to justify this categorisation, as reported by Need To Know.
Professor Chris Stringer, who is a research leader at the Natural History Museum and joint author of the paper, said: “In the context of Neanderthals and Homo sapiens we need to regard speciation as a gradual process that occurred over more than 400,000 years.
“It is correct that the two interbred where they were not geographically separate, but over time differentiation continued to a point where the two were distinctly different species.
“When the Neanderthals died out around 40,000 years ago the two species were in the final stage of the speciation process and were developing reproductive isolation from each other.”
“In the science of human origins implicit and unrealistic theoretical assumptions can be just as limiting as the scarcity of data,” added Dr Meneganzin, who is a post-doctoral fellow at KU Leuven.
“Taxonomic disagreement over the classification of our species and Neanderthals offer a prime example of oversimplified expectations regarding the nature of speciation.
“Both in present and past taxa, speciation unfolds across space and time, through multiple stages involving the incremental acquisition of distinct characters.
“By reading the fossil records through the temporal and geographic dimensions that shaped past human diversity, available data can become increasingly informative rather than more limiting and help move debates beyond unproductive deadlocks.”
Fossil records show that modern humans developed in Africa and neanderthals evolved in Eurasia.
Mapping over such a long period has proven challenging for scientists, due to interbreeding and exchange of genes and behaviours.
However, the study argues the two groups were already distinguishable species by the point interbreeding began.
To reliably trace modern human evolution, categorisations needs to be made about anatomical and geographical developments.
The study also claims that if interbreeding was the final word in determining species status, then hundreds of distinct species of mammals and birds today would have their separate species status revoked.
Without recognising patterns in evolution and subsequent categorisation, the question of when a species first appeared becomes more intractable.
Neanderthals were better equipped to cope with colder climates – an adaptation which modern humans have not yet fully developed without the use of technology.
They also had to be more physically active and for longer periods, in order to gather the resources they needed for survival.
This helps to explain morphological differences including ribcage and pelvis shapes inferring bigger internal organs such as the lungs, heart and liver – amongst a wide range of anatomical distinctions.
The more gracile skeleton of homo sapiens suggests a more economical physiology and less energy demand.
This could have made the difference between survival and extinction during rapid climate change or a strong competition for resources where the two coexisted.
