The Modern Human and His Distant Relatives

When the question of whether we are alone in the universe comes up in a conversation, we probably think in terms of aliens. But if we talk in terms of our species, it was not too long ago that the homo sapiens weren’t a monopoly, and several other human species roamed the earth. However, those days are long gone, and our closest relatives who are alive and well are the Great Apes, specifically the chimpanzees and bonobos with whom we likely share a common ancestor from roughly 6 to 8 million years ago.

Taxonomic Classification of Our Extant and Extinct Relatives (and Us)

Figure 1: Taxonomy of Homo sapiens and our closest relatives [source]

To understand our evolutionary ancestors better it might help to get some taxonomical terms out of the way. Beyond the modern human’s species (sapiens) which is exclusively our title to carry, and genus (homo) which extends to extinct human species, further up the rank we have our very own (but not quite) tribe called the Hominini. This is where the Great Apes enter the picture.

Chimpanzee [source]

We share the most similarities with Chimpanzees and Bonobos (genus: Pan), and as a result, we also share the Hominini tribe with them. The hominins are grouped along with gorillas (tribe: Gorillini) to form the Homininae subfamily, which in turn joins forces with orangutans (genus: Pongo, subfamily: Ponginae) to form a family called Hominidae. To summarise: the modern man belongs to the Hominidae family along with chimpanzees, bonobos, gorillas and orangutans with varying degrees of similarity. All that’s to say the classification is ever-changing, as made evident by a controversial study which claims that humans are more closely related to orangutans than chimps.

The plot thickens when we add other hominins, that functioned as a predecessor to the homo genus, to the mix. They belonged to a subtribe called Australopithecines which is a group of several (now-extinct) genera, of note being the Australopithecus and the Paranthropus genera.

Hominins and Their Interactions With One Another

The exact number of human species to have existed is still a mystery. A common misconception is that there was rarely any overlap between the periods and locations inhabited by them. If we go down the timeline roughly two million years, the Australopithecus africanusParanthropus robustus, and Homo erectus species appear to have inhabited the hills and caves near the Drimolen Paleocave System during the same period, although the levels of their interactions are still unknown.

Homo sapiens came into the picture roughly 200,000 years ago, at a time when other hominins such as the Neanderthals (Homo neanderthalensis) of Eurasia, and the Denisovans (homo denisova) of Asia existed. All three species were known to intermingle and interbreed with one another. Both the Neanderthals and Denisovans have a shared lineage as they had a common ancestor who existed roughly 390,000 years ago.

Denny – the Girl With a Neanderthal Mother and a Denisovan Father

Bone fragment of Denny from four angles Credit: Brown, S. et al/CC BY 4.0 [Source]

Scientists have discovered a 90,000-year-old bone fragment that belongs to a roughly 13-year-old female nicknamed Denny with a Neanderthal mother and a Denisovan father in the Denisova Cave in Siberia. The bone fragment was first identified as one belonging to a hominin by studying its collagen. By examining the DNA in the fragment’s mitochondria, the Neanderthal heritage of the mother was discovered. Finally, the nuclear DNA was reviewed, and two things were confirmed: the paternal lineage was Denisovan, and there was high heterozygosity (genetic diversity) indicating how genetically further apart the parents were – they were as apart as two different species would appear to be.

The Hobbits That Existed Outside of Lord of the Rings

Remains of the ‘hobbit’ (left) Credit: Equinox Graphics/SPL [source]

At a similar time, Homo florensis or the Hobbits inhabited Flores, an Indonesian island. Their existence can be traced back to 18,000 years ago and are our closest ancestors in terms of how recently they existed. It is estimated that they lived roughly 100,000 to 50,000 years ago, which is astonishingly close, and they may have been wiped out as a result of volcanic activity as made evident by some geological data. The species could have suffered from island dwarfism which would be a result of them inhabiting the island for a long time, and the island’s lack of food and predators. However, the possibility of them having short ancestors who migrated to the island also exists.

Modern Humans (Evidently)Outlived the Neanderthals

Homo neanderthalensis, adult male. Reconstruction based on Shanidar 1 by John Gurche [source]

The Neanderthals are one of the most extensively researched human species. Although they arrived in Europe 200,000 years before modern humans did, the latter evidently outlived the former. One theory suggests that although Neanderthals adapted to the chilly climate of Europe using warm clothes and superior hunting tools and techniques better suited to the woodlands, the climate change Europe underwent, which changed the landscape closer to that of African savannah terrain, took them aback as they could no longer sustain themselves without adapting again, which they failed to do. Modern humans were better suited for the adaption given their late entry into the continent and their wider range of hunting prey and better tools.

Hominins’ Evolution into an Omnivorous Tribe

Some theories suggest that the earlier hominins mostly relied on plants for their nutrition. Likely, the guts of early hominins were not adapted for meat, as they had a large caecum, and if they consumed meat, they might have suffered from stomach pain, nausea, bloating and possibly death. The inclusion of seeds and nuts into the diet may have allowed for the growth of the small intestine along with the shrinking of the caecum, which allowed for the hominins to experiment with meat. The main factor which pushed us towards a carnivorous diet was climate change, which resulted in fewer plants and a lot more prey. The switch from vegetarianism (with the occasional insect in their diet) to an omnivorous stance could have caused fewer and fewer hominins to exist due to competition. However, extinction is a consequence of evolution and while this is one factor to come into play, it was inevitable that at most a few species would come out on top, and homo sapiens did just that.

Sketch of purgatories [source]

There are some fundamentals questions we all have about ourselves as people and our place in the universe. The more we learn about our history and our relation with other organisms, the more we might realise we aren’t so different after all, just in case videos like this don’t make that apparent.

The Purgatorius, a rat-sized animal, was possibly being the oldest primate to have existed. Just 10 years ago, the Denisovans were discovered in the Denisova cave in Siberia after stumbling upon a pinky finger bone and three teeth. In 2015, another species called the Homo naledi was discovered in South America, and it is estimated that they lived between 335,000 and 236,000 years ago. I think it’s safe to say that there’s a lot more to be discovered about our lineage, and it would probably never cease to amaze.

Written by Shweta Manoharan