Where did we come from?
There is something about human evolution that is inherently intriguing; it sparks an innate curiosity about what preceded (and lived, died and bred with) our species, Homo sapiens.
But where in our ancestry does the “human” part of “human evolution” begin?
In other words, how far back in time do we have to go that our ancestors were not human and were, instead, apes walking on two legs? What does it take to be called “human”?
Getting to the bottom of it is trickier than it looks, says Tanya Smith, a human evolutionary biologist at Griffith University.
More than a century ago, scientists began classifying fossils according to whether they seemed to have looked and acted more in tune with humans living today – that is, us – than ancient hominids. , such as ape-like monkeys. Australopithecus afarensisnicknamed Lucia, who lived millions of years ago.
“Originally it was things like brain size, tool use – what we thought were characteristic specializations of humanity that would be different from earlier Australopithecines,” says Professor Smith.
In the years that followed, however, fossil discoveries overturned some of these assumptions.
So where are we?
Let’s start with the here and now. We, Homo sapiensare in the human bucket – we define what is human.
Have been supported by Macquarie Dictionarywhich states that a “human” is “a human being”, which, in turn, is “a member of the human race, Homo sapiens“.
Contrary to the Macquarie dictionary, however, we are not alone in the historical human bucket.
So, let’s take a look back at our evolutionary history and see where we end up.
Our closest cousins
Time travel a few tens of thousands of years, and there were other two-legged primates that looked a lot like us roaming the planet.
They included our closest cousins Neanderthal Homobetter known as Neanderthals, and a group that some consider to be a sister line of Neanderthals called the Denisovans.
Skeletons show that Neanderthals were muscular and a bit shorter than us, but had larger brains for their height. Denisovan’s portrait is fuzzier – the entire reported retinue of Denisovan fossils could be counted on two hands – but they probably looked like Neanderthals.
We don’t know much about the behavior of Neanderthals, but what’s increasingly clear is that they weren’t the finger-dragging, club-wielding idiots depicted in popular culture.
They made tools and art and engaged in symbolic behavior, creating objects that had uses beyond eating food.
“You can find … teeth that had been drilled potentially for wearing or adorning objects, and these are from sites that were really strongly associated with Neanderthals,” says Professor Smith.
“So it seems that some basic abstraction and symbolism was practiced, at least by later Neanderthals.”
Whether these behaviors originated with Neanderthal groups or were copied when they came into contact with Homo sapienswe don’t know, says Professor Smith.
Alongside fossils and other archaeological remains, traces of Neanderthals and Denisovans can be found today as stretches of DNA in our genome, remnants of interbreeding through the ages – not only with us, but also between them.
So, says Professor Smith, instead of thinking of the evolution of our species as a “family tree” – with branches splitting into two species, then splitting again or becoming a dead end – think of it instead as a braided river, where several water channels diverge, flow a little, then merge.
“It’s the idea that genetic information potentially mixes in certain populations, then splits, then later in time mixes again and splits again.”
These ancient encounters have prompted some researchers to suggest that the three types of humans should be considered the same species, said Australian National University evolutionary biologist João Teixiera.
What’s in a name?
Could the answer to our question be as simple as nomenclature?
The Homo part of our Latin name and that of the Neanderthals means “human” or “man”. Over the decades more members were added to the Homo kind, like Homo floresiensisperhaps better known as “The Hobbit”, and Homo naledi.
So would the first human be the first Homo?
Well…maybe, says La Trobe University archaeologist Andy Herries.
“If we define something like Homo, then we define it to be fundamentally more like us.
And yet, it is not without controversy.
“Strictly speaking, the oldest fossil that has been included in the genus Homo is 2.8 million years from Ledi-Geraru in Ethiopia“says Professor Herries.
“But a lot of people strongly disagree with that assessment. It’s half a mandible.”
What about cultural practices, like burying their dead, or symbolic representations?
“The behavioral evidence is patchy,” says Professor Smith.
“From that time they used tools, but we don’t know they used fire, and certainly we don’t think we bury their dead or create symbolic representations of things.
“It’s not until much later in the record that we get some of the things that we consider to be contemporary behaviors.”
The likely “first human,” she says, was homo erectus. These short, stocky humans have been a true pillar in the history of human evolution.
Estimates vary, but they are thought to have lived between 2 million and 100,000 years ago and were the first humans to leave Africa and enter Europe and Asia.
They are credited with abstraction, as evidenced an engraved seashell half a million years old.
Neanderthals, H. sapiens and the Denisovans are considered by some to have evolved from H. erectus populations in different parts of the world: Neanderthals in Europe, H. sapiens in Africa, and possibly Denisovans in Asia.
Case closed, right?
Well… even that is tricky, because there is an older Homo that H. erectus.
To meet Homo habilisor “handyman”, named because fossil remains have been found near a plethora of stone tools.
It appeared on the scene about 300,000 years before the earliest known H. erectusand its placement in the genus Homo has been controversial, to say the least.
Some researchers suggest it resembles an ape enough to be moved to older Australopithecines, which would strip it of its human or Homo Name.
At this point, we have traveled back a few million years in human history. Fossilized remains from then and before are incredibly rare, and what is unearthed tends to be in pieces.
“You rarely get a full suite of evidence in a single individual. So you’ll have a bit of a skull and then you’ll have a bit of a hand and you’ll have a bit of a pelvis and you’ll have a few teeth, but we don’t know how they fit together. join,” says Professor Smith.
“It is only later in the fossil record that we have good, full rest of one homo erectus.
“Then you have sites where we know we had several people living at the same timebut [the fossils and artefacts] don’t come with tags when you take them out of the ground.”
Plus, there’s the gradual nature of evolution itself, says Professor Herries.
“There are so many different aspects of what makes us human, but they don’t all happen at once – it never happens.
“[Walking upright] usually comes first, then potentially stone tools, then we get big brains, which shouldn’t really be a big surprise because stone tools give you access to a much wider range of resources, and that helps your brain grow.
So, although there is no absolute line in history with humans on one side and apes on the other, Professor Herries agrees that the first human by contemporary measurement was probably a Homo erectus.
“There was a big evolutionary step that happened about 2 million years ago to 1.8 million years ago, at this shift to homo erectus, which evolves into more complicated stone tools and behaviors. They were the world’s first travelers.
“They did a lot of things for the first time.”