Are we really Homo sapiens?

Today we suspect that the chimpanzee is our closest relative, but it would be wrong to say that we descended from the chimpanzee. The two of us have only common ancestors. Somewhere in the distant past the paths of our development separated – and humanity’s further way could well have been much more complex than we thought.

Homo sapiens, Neanderthal, Denisova human, Homo erectus, Homo floriensis and many other intermediate forms seem to have existed successively and even side by side.

So far it has been assumed that only Homo sapiens survived the times. The reasons for this were sought in his reproductive system or in the development of a more complex, better functioning form of society – in short, in his superiority.

New studies, however, put many aspects into question. Perhaps the Neanderthal was in no way inferior to Homo sapiens. And perhaps it is not really true that only Homo sapiens survived…

First of all: What is a homo sapiens?

The first thing we should ask ourselves is what a Homo sapiens (wise man) is. – Already here the uncertainty begins.

The term was first used by the Swedish scientist Carl von Linné, when in 1735 he assigned the human being to the animal kingdom in his writing Systema Naturæ and to the genus Homo. But he renounced descriptions and wrote only ‘know yourself’. He thought that everyone knows what a human being is after all. In 1959, the botanist William Thomas Stearn then declared Carl von Linné to be the lectotype of the species Homo sapiens, i.e. the standard for determining whether an individual is a member of the human race. The mortal remains of Carl von Linné in Uppsala thus became the nomenclatural type of the anatomically modern human being. Anyone who looks like the northern European Linné is a human being.

Whether this definition is tenable is questionable.

The prevailing scientific opinion today assumes that anatomically modern humans developed in Africa and replaced other human species. This was accompanied however by mixtures and gene flows.

Neanderthal genes can be found in all populations outside sub-Saharan Africa, in Southeast Asia traces of the Denisova human were found and in African genes survive traces of another unknown human species, a “ghost ancestor” without fossil evidence.

This mixture of DNA seems to have been extremely useful for modern humans and has not only helped them to adapt to the newly found environment in the respective regions he invaded, but above all provided protection against local infectious diseases. One might therefore think that those who did not have the necessary share of Denisov or Neanderthal in the concerned region, became extinct for the most part.

The question arises as to how a mixture of “human species” could have been possible. It can also be asked under which term the resulting mixture of human beings should be defined.

Strictly speaking, so far there is no generally valid definition of the term “species” that meets the requirements of all biological disciplines equally. It is assumed that those who can mate and produce fertile offspring belong to a common species. However, the fact that a mixture between two species and the emergence of fertile offspring is also possible is shown with large cats. Since their chromosome number is the same, lion and tiger can mate. Female ‘ligers’, i.e. the cross product of a male lion and a female tiger, are usually fertile – in contrast to male ligers – and can mate again with one of their parent species.

Here it is important to note that in Homo sapiens the genes of female Neanderthals are found – but not those of male Neanderthals. The situation therefore seems very similar to that of tigers and lions.

The expression of genes seems to depend on the individual parent of the allele. In the animal kingdom, for example in large cats and equidae, the following can be observed:

If the bigger kind provides the mother, the offspring become bigger than the parents (mules, liger), while if the smaller type provides the mother the children become smaller and the death rate of the foetuses is very high (Tiger-lion, mules).

It makes therefore a difference both who mates with whom and also in whose family the offspring grows up and looks for its new partner. In any case, however, such a mixture is possible and for humans it is proven in studies.

It seems that only (bigger) female Neanderthals and male modern humans mixed with good success and that male foeti were rejected.

But who are we then?

If every one of us who reads this article wonders what he is, the answer is almost always ‘a half-breed’.

The starting point of the journey of the creation of the human being seems to have been Homo erectus 1 – direct ancestor of the Neanderthal, the Denisova human and the African modern human. An African ghost species, whose gene flows can be detected in Africa but nowhere else, has not yet been identified, but we can call it Homo erectus 2.

It can be assumed that hardly any of the people living today are “pure-bred”, i.e. free from genetic influences of a second human species, and that this is precisely what has ensured survival – evolution takes a decidedly positive view of hybrids. The purpose of mutation is adaptation and therefore survival. According to current knowledge, however, at least every human being descends from a common type of ancestor, Homo erectus.

According to his type specimen (white Central European, Carl von Linné), Homo sapiens is a hybrid between the African descendant of Homo erectus (modern man) and the Eurasian descendant (Neanderthal).

This gives rise to questions. First of all: Are we all Homo sapiens or just those of us that are Neanderthal hybrids? Should one not better change the type specimen of Homo sapiens and if it is no longer Linné, then who is it? Or are the Neanderthal, the Denisova man and Homo erectus 2 not own species, but only subspecies of Homo erectus (and with that Linné just one exemple of it)?

Perhaps the best answer to this question should be:

We are all Homo erectus, because we can all have fertile offspring among ourselves. Separations into separate human species have largely been reversed in the course of development and have only provided us with a few individual extra genes.

Noah’s Ark and more? – Catastrophic events once seems to have changed humankind

After all the above, the question arises as to what we can infer from this mixture, regardless of the genetic advantages it has brought us. And the answer could well be that there must have been a hidden catastrophe in the history of creation of humanity.

Let us once again briefly list the known genetic influences between the different human types:

  • Europeans: Modern man oo Neanderthals
  • Asians: Modern Man oo Neanderthals oo Neanderthals oo Neanderthals
  • Polynesians: Modern man oo Neanderthal oo Denisova
  • African: Modern man oo Homo erectus 2 (ghost species)

It turns out that the continent of Africa, in contrast to all other continents, possesses a high genetic variance, which speaks for a very long existence of its population. For all other continents, a lower initial population must be assumed, which has been called the bottleneck.

Since fossil human predecessors have been found, one has to ask oneself what happened and why humans only seem to have reproduced extensively in Africa.

Let us take the trouble to trace the genetic connections step by step and in detective detail work, even if we can only present the current state of knowledge here and science develops rapidly in this field:

Point Zero of Creation: Homo erectus 1 originates from a common ancestor with the chimpanzee and the bonobo, either in Africa or in Southeast Europe. At that time there lived monkeys on both continents. It divides into Homo erectus 1 in Africa and Homo erectus 2 in Eurasia.

Step two: Over a long course of time, Homo erectus 1 in Africa develops into a modern human being. He/she also lives in the Levant and the Middle East. Also from Homo erectus 1 develops in Eurasia the Denisova human and the Neanderthal.
Homo erectus 2 could have existed as another population and this could be the African ghost population or the one that can be detected as gene flow from the outside in the genome of Denisovan humans (Indian Homo erectus?). This is not yet certain. Denisovan humans and Neanderthals also mingle in East Asia about 100,000 years ago.

Step three: About 40,000 years ago (the dates re still debated) a sudden migration began:

  • The Neanderthal reaches the Middle East in small groups and mixes with modern humans. Due to the small genetic traces, however, these “returnees” could not have been many. In Eurasia the Neanderthal even dies out.
  • The Denisovan human persists only as a hybrid with Neanderthals in East Asia. Due to the small gene traces the population could not have been very large.
  • The Homo erectus 2, coming from Eurasia, reaches the modern human in Africa and is absorbed by its population. Due to the small traces also these returnees could not have been many. In Eurasia the Homo erectus 2 dies out.

Step four: The hybrid Neanderthal/modern human (without gene traces of Homo erectus 2) spreads all over Eurasia. In Polynesia he also mixes with the descendants of the Neanderthal/Denisova hybrids.

What do we deduce from this history hidden in our genes?

It turns out that Homo erectus could originally have been living throughout Eurasia and Africa, where it was genetically highly diversified and divided into different species due to geographical distance and different living conditions.

But then, at some point, there was a real flight from the West Eurasian area, with the extinction of human life in that region. Only residual groups of the original populations survived and, due to their small size, mixed or merged with the still existing large and diverse African population of modern humans or with modern humans living in the Levant.

This means that there must have been an event that almost extinguished humankind in these places. This event only affected the West Eurasian region, but not Africa and East Asia.

Such catastrophes could even have occurred several times, because the Neanderthals, but not the Denisovan people living in Asia, went through a genetic bottleneck after the separation from the ancestors of the Denisovan population. The analysis of the mtDNA of Neanderthals shows a strong genetic impoverishment. There were fewer of them.

So – What catastrophic event almost wiped out entire human species?

The eruption of the Toba volcano in Sumatra about 74,000 years ago and the resulting shock-like short ice age is among other candidates held responsible for the first extinction of humans in Europe.

For the second death wave, which has left its traces in our DNA, a combination of the last ice age and the eruption of the volcano under the Phlegraean fields and Vesuvius (Campanian Ignimbrite) can be considered. It is unlikely that it was only the ice age, since the glacial peak of the last ice age occurred long after the extinction of the Neanderthals (Vistula cold period) and hybrids of modern man / Neanderthals survived this peak well in Europe. It is also unlikely that they were infectious human diseases, as later encounters with other populations led to mixing rather than extinction. Vesuvius, which threatens Europe again today, is therefore a particularly worrying top candidate for the cause of extinction.

One fact becomes clear after all the above: the small proportion of archaic populations in our genes is due to the small number of surviving individuals and the infertility of male hybrids after the catastrophes, not to the Neanderthal or Denisova-people being inferior to Homo sapiens.
And the extinction of the human population of an entire continent could happen again at any time. Here in Europe or elsewhere in the world.

Could we divide into several human species again?

It is not impossible that we could be different species again one day if separating circumstances and adaptations to the environment would encourage this. A mere separation on the basis of geographical conditions is unlikely in times of globalisation, but perhaps the progressive mechanisation combined with the abilities of the individual will lead to a change and possibly even to separation into several human species.

There could also be a targeted evolution. Gene modification and medical interventions could optimize and modify humans. This could hypothetically be linked to the surprising evolution factor ‘purchasing power’ of the individual. Those who can pay for it could become healthier, more beautiful and more intelligent, perhaps in the future they would be connected to the Internet by microchips and thus smarter, perhaps they would be bigger, more muscular or more durable by changing their genes.

The current debate on bioethics raises the question of whether it is permissible to design the catalogue of genes that we want for our children…. It must be assumed, however, that genetic engineering will follow the path of self-directed optimisation. Evolution will prevail. Humans will become creators. We are therefore perhaps on the threshold of a process of self-determination, of controlled evolution. According to the palaeontologist Antonio Rosas, this could even lead to the emergence of a new human race.

However, when we see what humans breed out of dogs, cats and horses for nonsensical, nonviable creatures, a natural evolution might well be the much better alternative though.

U.C. Ringuer / C. Voigtmann

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