Three findings in recent days have just changed what we knew about the origin of the human race and of our own species, Homo sapiens. It is possible – some experts say – that we should discard this concept to refer to ourselves since these discoveries suggest that we are a Frankenstein with pieces of other human species with whom not so long ago we shared a planet, sex, and children.
This week’s findings assume that around 200,000 years ago there were as many as eight different human groups or species. All were part of the genus Homo, which includes us. The newcomers show an interesting mix of primitive features – huge arches on the eyebrows, flatheads – and modern.
The dragoman of China had a cranial capacity as great as that of present-day humans or higher. The Homo of Nesher Ramla, found in Israel, could be the one that originated the Neanderthals and Denisovans who occupied Europe and Asia respectively and with whom our own species had repeated sexual encounters from which mestizo children were born who were accepted in their respective tribes as one more.
Now we know that through those crosses all people from outside Africa carry 3% Neanderthal DNA or that the inhabitants of Tibet have genes to be able to live at high altitude that the Denisovans passed on to them. There is something much more disturbing that genetic analysis of present-day New Guinea populations has revealed: Denisovans – a sister branch of Neanderthals – may have lived until just 15,000 years ago, a breath in evolutionary terms.
The third big find in recent days is almost detective. DNA preserved in the Denisova cave floor in Siberia has been analyzed. Genetic material has been found from indigenous humans, Denisovans, Neanderthals, and Sapiens in periods so close that they could even overlap. The remains of the first known hybrid between human species were found here three years ago: a girl daughter of a Neanderthal and a Denisovan.
Paleoanthropologist Florent Detroit discovered for science another of these new human species: the luzonensis Homo, who lived on an island of the Philippines 67,000 years ago and showing a mixture of strange traits that might result from its long evolution in isolation for more than a million years.
It is something similar to what his contemporary Homo floresiensis , or Flores man, experienced, a five-foot human who lived on an Indonesian island. It had a brain the size of a chimpanzee, but if the intelligence test most used by paleoanthropologists is applied to it, we can say that it was as advanced as sapiens, since its stone tools are just as evolved.
These two island inhabitants are joined by Homo erectus, the first traveling Homo that left Africa about two million years ago. He conquered Asia and lived there until at least 100,000 years ago. The eighth passenger in this story would be Homo aliens, a fossil found in China with a mixture of Erectus and sapiens, although it is possible that it will eventually be assigned to the new lineage of Homo long.
“I’m not surprised there were several human species alive at the same time,” explains Detroit. “If we consider the last geological period that began 2.5 million years ago, there have always been different genera and species of hominids sharing the planet. The great exception is today, never before had a single human species existed on Earth ”, he acknowledges. Why are we sapiens the only survivors?
For Juan Luis Arsuaga, Atapuerca paleoanthropologist, the answer is that “we are a hypersocial species, the only ones capable of building ties beyond kinship, unlike other mammals.” “We share consensual fictions like country, religion, language, soccer teams; and we came to sacrifice many things for them ”. Not even the human species closest to us, the Neanderthals, who did create ornaments, symbols, and art, did not behave like this. Arsuaga sums it up like this: “Neanderthals had no flag.” For reasons still unknown, this species became extinct about 40,000 years ago.
Sapiens was not “strictly superior” to their fellow human beings, says Antonio Rosas, a paleoanthropologist at the CSIC. “Now we know that we are the result of hybridizations with other species and the set of characteristics that we have turned out to be the perfect one for that moment,” he explains. A possible additional advantage is that the sapiens groups were more numerous than the Neanderthals, which means less inbreeding and better health of the populations.
Detroit believes that part of the explanation is in the very essence of our species sapiens, sage in Latin. “We have a huge brain that we must feed, so we need a lot of resources and therefore a lot of territories,” he says. ” Homo sapiens experienced a huge demographic expansion and it is quite possible that the competition for territory was too harsh for the rest of the species,” he adds.
María Martinón-Torres, director of the National Center for Research on Human Evolution, believes that the secret is “hyperadaptability.” “Ours is an invasive species, not necessarily malicious, but we are like Attila’s horse of evolution,” he says. “As we go along and with our lifestyle, biological diversity decreases, including human diversity. We are one of the ecological forces with the greatest impact on the planet and that history, ours, began to take shape in the Pleistocene [the period that begins 2.5 million years ago and ends about 10,000 years ago, when sapiens is already the only species human remaining on the planet] ”.
The findings of a few days ago again pose a growing problem: scientists increasingly name more human species. Does it make sense to do it? For Israel Hershkovitz, Israeli paleoanthropologist author of Nesher Ramla’s Homo finds, no. “There are too many species,” he says. “The classical definition says that two different species cannot have fertile children. DNA tells us that Sapiens, Neanderthals, and Denisovans had them, so they should be considered the same species ”, he points out.
“If we are sapiens, then those species that are our ancestors through mixing are also so”, João Zilhão, ICREA professor at the University of Barcelona.
This is a matter of confrontation between experts. José María Bermúdez de Castro, co-director of Atapuerca, recalls that “hybridization is very common in current species, especially in the plant world.” “The concept of species can be nuanced, but I think we cannot abandon it because it is very useful to understand each other.”
Many nuances come into play here. The obvious differences between sapiens and Neanderthals are not the same as the identity as a species of Homo luzonensis , of which only a few bones and teeth are known, or of Denisovans, from which most of the information is derived from DNA extracted from fossils tiny.
“Curiously, despite the frequent crossings,” explains Martinón-Torres, both sapiens Neanderthals they have been perfectly recognizable and distinguishable species until the end ”. “The features of the late Neanderthal are more marked than those of the previous ones, instead of being blurred as a result of crossing.
There were biological exchanges, and it is possible that also cultural, but none of the species ceased to be, distinctive, recognizable in their biology, its appearance, its specific adaptations, its ecological niche throughout its evolutionary history. I think this is the best example that hybridization does not necessarily collide with the concept of species ”, he concludes. His colleague Hershkovitz warns that the debate will continue: “We are excavating three other caves in Israel where we have found human fossils that will provide a new perspective on human evolution.”