This is a complicated question. Denisovans are actually a hybrid species made up of at least three different species of archaic hominids. Around a million years ago, there was a “copying error” in the brain of one particular subspecies of Homo Erectus. This led to increased intelligence, and by 800,000 years ago this advanced group created an advanced acheulian stone technology and spread out over the whole of the Old World.
Their original habitat may have been the hills of Northern India, because this is the earliest example of such technology and it seems to spread in all directions from the river systems there.
In Europe, they assimilated (absorbed) Homo Antecessor and became Classic Neanderthals. In China, they assimilated the related Peking Man. This is why pre-Neanderthal Europeans more resemble the DNA of Denisovans than Neanderthals: one of the three species which make up Denisovans is actually the species of which Peking Man and Antecessor were a part.
In Africa, the advanced Homo erectus absorbed Homo Ergaster and eventually became the four to five subspecies which merged to form Anatomically Modern Homo Sapiens between 300 and 200 thousand years ago.
This may seem complicated, but we must think of human evolution, and probably all evolution, as waves of assimilation. A species spreads out and adapts to niches, becoming various subspecies. Eventually, several subspecies become successful enough to spread out, or climate change favors one or the other. As they spread out, they hybridize with other subspecies and gain hybrid vigor. They continue to assimilate all the other subspecies until the collective genome becomes a new species with new subspecies.
The old idea of a tree or even a Bush is mostly incorrect. These “species” are better thought of as waves.
Advanced Homo Erectus or Early Archaic was A wave that assimilated most subspecies of Homo Erectus, and became Neanderthal in Europe, Homo Sapiens in Africa and the Middle East, Denisovans in Asia, the Mystery Hominid in SE Asia, and the Microcephalin D Hominid in India.
Only a few species escaped this wave of assimilation, and survived in Island Asia and the most remote parts of Africa.
Denisovans are a hybrid of a Neanderthal Sister species, Peking Man, and a more basal species that lived mostly in SE Asia.
Later, Neanderthals assimilated Denisovans and most of the Homo Sapiens living in SW Asia. Later still, a hybrid of Neanderthals and Homo Sapiens assimilated Neanderthals. Later still, mostly Homo Sapien agriculturalists assimilated the hybrids, as well as remaining Denisovans any other surviving subspecies like the aforementioned varieties in SE Asia and remote areas of Africa.
Waves.
consider this:
everyone in the world has a little bit of Neanderthal. Tibetans, SE Asians, and Native Americans have some Denisovan. Some SE Asians and ZPakistanis also have a bit of a species which branched from is 3.1 million years ago, the same time as our final separation from chimps and the appearance of the genus Homo (Homo Habilis).
The only people without Neanderthal are a few groups of hunter gatherers in Africa. However, these groups have introgression from a species which branched off from us 800,000 years ago and another that branched off 1.3 million years ago, about the time we lost our fur.
Pure Homo sapiens do not exist. We are hybrids too.
Although the above is complicated, it’s actually a gross simplification and lacks citations. I go much more in depth on my blog.
Toward a More Logically Acceptable Model of Archaic Introgression
From my Qora questions:
https://www.quora.com/What-do-we-know-about-Denisovans-How-closely-related-are-they-to-Neanderthals/answer/Joseph-Layden?__filter__=&__nsrc__=2&__snid3__=4415800248
Their original habitat may have been the hills of Northern India, because this is the earliest example of such technology and it seems to spread in all directions from the river systems there.
In Europe, they assimilated (absorbed) Homo Antecessor and became Classic Neanderthals. In China, they assimilated the related Peking Man. This is why pre-Neanderthal Europeans more resemble the DNA of Denisovans than Neanderthals: one of the three species which make up Denisovans is actually the species of which Peking Man and Antecessor were a part.
In Africa, the advanced Homo erectus absorbed Homo Ergaster and eventually became the four to five subspecies which merged to form Anatomically Modern Homo Sapiens between 300 and 200 thousand years ago.
This may seem complicated, but we must think of human evolution, and probably all evolution, as waves of assimilation. A species spreads out and adapts to niches, becoming various subspecies. Eventually, several subspecies become successful enough to spread out, or climate change favors one or the other. As they spread out, they hybridize with other subspecies and gain hybrid vigor. They continue to assimilate all the other subspecies until the collective genome becomes a new species with new subspecies.
The old idea of a tree or even a Bush is mostly incorrect. These “species” are better thought of as waves.
Advanced Homo Erectus or Early Archaic was A wave that assimilated most subspecies of Homo Erectus, and became Neanderthal in Europe, Homo Sapiens in Africa and the Middle East, Denisovans in Asia, the Mystery Hominid in SE Asia, and the Microcephalin D Hominid in India.
Only a few species escaped this wave of assimilation, and survived in Island Asia and the most remote parts of Africa.
Denisovans are a hybrid of a Neanderthal Sister species, Peking Man, and a more basal species that lived mostly in SE Asia.
Later, Neanderthals assimilated Denisovans and most of the Homo Sapiens living in SW Asia. Later still, a hybrid of Neanderthals and Homo Sapiens assimilated Neanderthals. Later still, mostly Homo Sapien agriculturalists assimilated the hybrids, as well as remaining Denisovans any other surviving subspecies like the aforementioned varieties in SE Asia and remote areas of Africa.
Waves.
consider this:
everyone in the world has a little bit of Neanderthal. Tibetans, SE Asians, and Native Americans have some Denisovan. Some SE Asians and ZPakistanis also have a bit of a species which branched from is 3.1 million years ago, the same time as our final separation from chimps and the appearance of the genus Homo (Homo Habilis).
The only people without Neanderthal are a few groups of hunter gatherers in Africa. However, these groups have introgression from a species which branched off from us 800,000 years ago and another that branched off 1.3 million years ago, about the time we lost our fur.
Pure Homo sapiens do not exist. We are hybrids too.
Although the above is complicated, it’s actually a gross simplification and lacks citations. I go much more in depth on my blog.
Toward a More Logically Acceptable Model of Archaic Introgression
From my Qora questions:
https://www.quora.com/What-do-we-know-about-Denisovans-How-closely-related-are-they-to-Neanderthals/answer/Joseph-Layden?__filter__=&__nsrc__=2&__snid3__=4415800248
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