Scientists are in the process of identifying the missing pieces in the evolution theory, thanks to the discovery of a supposed interbreeding scenario between pre historic European Neanderthals and African Hominins. For hundreds of years, Neanderthals have been deemed as the loophole between primates and the Homo sapiens sapiens (modern man). Recent research conducted by scientists from the Max Planck Institute for the Science of Human History, in collaboration with the University of Tübingen recovered generic data that postulates a timeline for a suggested hominin migration from Africa to Europe after Neanderthal ancestors arrived in Europe by a descent that is similar to that of modern man.
The working theory stipulates that the Hominins from Africa interbred with Neanderthals in Europe, leaving traces of themselves on the mitochondrial DNA of the Neanderthals. This follows the fact that mitochondrial DNA exists in the mitochondria, which can only be passed down from mother to child.
The Mitochondrial DNA
Mitochondria are organelles which are present in body cells that convert food into energy. They are therefore the energy producing machines that convert nutrients and oxygen into adenosine triphosphate (ATP); energy that can be used by the body.
The mitochondria have a unique DNA, which is different from the nuclear DNA that can be used to mark out population split time frames as well as maternal heredities. More so, a change in the mitochondrial DNA as a result of mutations aids the estimation of elapsed time frame since separate individuals shared a common predecessor and also in the distinction of two groups because the changes that arise from mutations are predictable.
Neanderthals and the Modern Man
In the recent past, researchers analysed Neanderthal DNA in comparison to that of modern man and concluded that a split of the two species occurred in an estimated time frame of between 765,000 to 550,000 years ago. In contrast, the recent studies encompassing the mitochondrion DNA extracted from an ancient Neanderthal femur, exhumed in Germany at the Hohlenstein-Stadel cave, suggests a possible era which reduces the timeframe of the split between the two groups to 400,000 years ago.
The findings of the research showed that the mitochondrial DNA of humans is highly similar to that of the Neanderthals. However, prior studies suggested a closer relationship between the Denisovan species as compared to modern man, a conclusion that again illustrates a flawed conclusion based on past findings.
The inconsistencies drawn from this research spurred a debate that led to a proposed theory, which suggests that a migration of hominins from Africa may have happened just before the dispersion of modern man. The hominin group, which is closest in ancestry to modern human, is likely to have interbred with the Neanderthals in Europe, thus introducing their mitochondrial DNA, and fragments of their nuclear DNA to the Neanderthals using genetic admixture.
These claims were heavily backed by the excavated Neanderthal femur in Germany, which offered genetic data that is very different from that of other Neanderthals studied in the past. Scientist tagged this particular Neanderthal the HST. Although radiocarbon dating did not work to determine the age of the bone, the mutation rate estimated an approximate value of 124, 000 years ago.
The genetic data collected suggests a different mitochondrial ancestry to those of other discovered Neanderthal remains. A comparison of the HST and other Neanderthals showcase a split timeline of a minimum 220,000 years. The generic information also reveals an extensive genetic margin regarding diversity amongst the Neanderthals.
The Mysterious Hominin Migration
Findings from the researchers propose a workable scenario that strives to fill in the gaps. These scientists theorise a situation where hominins migrated from Africa to Europe and introduced their mitochondrial DNA to Neanderthals before the separation of Neanderthal and human DNA approximately 470,000 years ago.
These events are also assumed to have happened before other Neanderthals including the HST dispersed about 220,000 years ago.
An influx of hominins that may have resulted from the migration is responsible for the minimum impact on the Neanderthal population of Europe. However, it caused a significant amount of impact on their mitochondrial DNA by completely replacing it.
Johannes Kraus, one of the scientists at the Max Planck Institute for the Science of Human History, and senior author of the research says that the proposed scenario settles the differences in both mitochondrial and nuclear DNA of pre historic hominins. “It also accounts for the inconsistencies in the study regarding the modern human and Neanderthal population split timelines” She adds.
While distinctive genetic data is hard to obtain given the fragile nature of nuclear DNA to contamination, nuclear DNA from the HST femur would be vital in ascertaining these assumptions, as well as outlining clear genomic relationships that exist between the hominin, Neanderthal and modern human populations. These new findings have spurred more insight to future study.