Table of Content1. Introduction |
Introduction
We all know what evolution is and how it generally works, but how much do you know about how we evolved? The story of human evolution isn’t one that’s taught in much detail, yet it’s one of the most important because it’s our story. It also offers valuable insight into how our bodies and minds were formed, and how we changed to become the most intelligent and productive species on planet Earth.
If you want to learn more about how humans have evolved over millions of years, you’ve come to the right place. As you can imagine, it’s a big topic to cover, so we’ve referenced other materials for those who want to dig deeper into the origin of humanity. We’ve also split the guide into several easily digestible parts:
- What Were Early Humans Are?
- The Process Of Evolution
- How Did Humans Evolve?
- Human Evolution Timeline
- Are Humans Still Evolving Today?
Those five sections allow us to cover human evolution without getting lost in the minutiae or using terminology that’s difficult to understand. You won’t need a degree in paleoanthropology – the study of human evolution – to understand this guide.
Let’s get started at the beginning with early humans. What were they like?
What Were Early Humans Like?
Choosing a starting point to talk about human evolution is tricky. Do we start with single-celled organisms? The earliest primates? The unknown missing link between monkey and mankind?
There are many steps in the evolutionary process we could choose to begin our journey. Single-celled organisms and primates aren’t humans, so we’re going to start with the first early humans – the first beings belonging to the Homo genus.
The Homo genus emerges from the Australopithecus genus, which was largely based in eastern and southern Africa. The genus name references their distribution, being Greek for “southern ape.” Apes aren’t humans, so that’s why we’re starting with the Homo genus instead.
As for the first species in the Homo genus, that would be the Homo habilis, or “handy man” in English. As is common with the process of scientific discovery, we don’t know if they were definitely the first, they’re just the earliest that we have found evidence of.
So, how did they live? The Homo habilis lived in the Early Pleistocene, which was a period 2.3 to 1.65 million years ago. Their place in the Homo genus has been debated since they share many similarities with an Australopithecus genus species, specifically the Australopithecus africanus.
The H. habilis differed from australopithecines in that they created and used Oldowan tools, primarily for butchering meat. They ate more meat than australopithecines, which played a vital role in human evolution. Those tool-making and dietary differences solidified the H. habilis as the first of the Homo genus for much of the paleoanthropological community.
They were thought to travel the African savanna in groups numbering between 65 to 85, ensuring they had enough manpower to fend off predators like crocs and big cats.
How Long Have Humans Existed?
The evolutionary journey of humankind spans many millions of years, so once again we need to establish what we mean by humans. We have a timeline of the entire human evolutionary journey later on in this guide. From now on, any mention of members of the Homo genus will be referred to as early humans.
While Homo translates to man and its genus members are often referred to as human, what we think of are specifically Homo sapiens. That’s because we’re the only extant species of the genus, the others are all extinct. You’ve probably heard that name before because it’s yours! It means “wise man,” as a clear reference to our status as the smartest of the primates.
So, how long have H. sapiens existed? By all accounts, we seem to have emerged from at least 200,000 years ago, though some other discoveries of tools could push that back to 300,000 years ago. When the journey to get here has spanned tens of millions of years and considering how much humanity has done in just the last 6,000 years, a few hundred thousand years isn’t that long.
As for the distribution of H. sapiens across the world, we have estimated that the first humans settled Australia as little as 60,000 years ago while the Americas were settled later, predicted to be 13,000 years ago, by crossing the Bering Strait land bridge.
The Process Of Evolution
Now that we know about the first early humans (to the best of our abilities), we should take a break to tackle the process of evolution. Then we can apply those processes to human beings to explain how they evolved from the Homo habilis to us, the Homo sapiens of today.
Explaining evolution in fine detail would be its own guide, if not several, but we can nail the fundamentals right here and explain them in a way that everybody understands.
In a guide about evolution, it was only a matter of time until Charles Darwin showed up. While the general ideas surrounding the all-encompassing process of evolution showed up earlier, like in the writings of philosopher Herbert Spencer, the current theory was mainstreamed with Charles Darwin’s On the Origin of Species in 1859.
The publication outlined the process by which evolution pushes certain species forward while leaving others in the dust – natural selection. As the name suggests, this is where the environment and other circumstances pressure a species into making gradual changes over many, many years.
The process is often taught in five steps, called VISTA:
- V – Variance
- I – Inheritance
- S – Selection
- T – Time
- A – Adaptation
Let’s explain what these mean since they’re the secret to natural selection, and so the process that evolution uses to develop lifeforms.
First, variance. These are the naturally occurring differences inherent to the species of our planet, even relatively similar ones, and on the genetic level, individual members of those species are different, too. The level of variance in nature is astounding and serves as the perfect hotbed for mutations in those beings.
Inheritance is where beings reproduce, producing genetic copies of themselves by typically mixing DNA, inheriting features from both parents. This is commonly observable through different traits, like height, eye color, and certain face shape features, like the nose.
Through this repeating process of DNA inheritance, selection takes place. This is where certain inheritors of certain DNA profiles are better equipped to survive. Resources are limited, after all, so the world is a competition between animals to survive and ensure they reproduce. The more successful a species is at finding food, mating, and fighting back against or avoiding predators, the better chances they have to survive. Seemingly trivial details can change how a being interacts with its environment.
This process of gradual mutation takes a lot of time as species reproduce. When subject to the same environmental pressures, the species will either compete and become dominant or die out from lack of survival, now that they’re being outcompeted. This process takes hundreds of thousands of years.
Finally, adaptation is where the majority of a species has now transitioned into the newer form. Its genetic material has gradually altered with each generation and is now the predominant expression of that species on Earth. As we’ll see with human evolution, it’s then common for the old variants to die out and the new species to continue with success.
How Did Humans Evolve?
Now that we know the evolutionary process and how it takes place, do we know how it happened with humans? As we’ve already discussed, the making and use of rudimentary stone tools were instrumental to the continued evolution of man, as was the higher intake of proteins that came from eating more meat and eventually learning to cook it.
Homo Habilis & Homo Erectus
Those were the main distinctions that differentiated the Homo genus from the Australopithecus, although we have since discovered evidence for Australopithecus using tools too. Alongside the Homo habilis, there was also the Homo rudolfensis that lived approximately 1.9 million years ago and the Homo erectus, which had a long span of life from 1.8 million years ago to as recent as 100,000 years ago, during which they ranged from Southern Africa to East Asia. H. erectus is commonly synonymized with H. ergaster, they’re the same species. They’re also the most successful of the Homo genus to date since they lasted the longest, even longer than we Homo sapiens have existed right now.
So, what were the meaningful differences between H. habilis and H. erectus? They are thought to have lived beside one another and we are unsure if erectus evolved from habilis or if they had a shared Australopithecine ancestor. The erectus were the first early humans to leave Africa and control fire. Controlling fire is very important, as you no doubt know, but the ability to cook may have made our brains larger, giving us those wrinkles that increase the surface area of our brain.
As for why the environment seemed to select early humans that became smarter and more tactical over time, we can only guess. When these earliest of the Homo genus were forming, they were subdued to swinging climate circumstances that required adaptability and resourcefulness. The H. erectus were relatively unchanged due to their control of fire, allowing them to brave colder climates, so they adapted behaviorally instead. Their brains were only 75% as large as ours and they looked virtually identical to us except for the head, which had a prominent brow ridge and a sloping forehead.
Homo Antecessor & Homo Heidelbergensis
Starting around 1.2 million to 800,000 years ago, we initially discovered them in Spain and had long theorized that they were the common ancestor of Homo sapiens and Neanderthals, which we’re getting to in just a moment. However, the same is also said of the Homo heidelbergensis, which started 800,000 years ago. Transitional Homo fossils after the 800,000-year mark are typically marked as H. heidelbergensis.
The H. heidelbergensis can generally be described as a mix of the H. erectus and H. sapiens in terms of their inherited traits. Their brain size was the closest to ours after the continued tool use and fire taming of the erectus and transitional species. It was the heidelbergensis who are thought to have first propagated through Europe, too, and seemed to be capable of coordinating hunting strategies with manufactured spears and other sharp implements.
Their dietary requirements would have required a lot of carbohydrates, which Europe was great for in terms of edible plant matter, and they may have engaged in art through engraving although the symbolic nature of specimens is disputed.
There were also geographic offshoots and subspecies like Homo rhodesiensis and Homo floresiensis that are thought to be tied to H. antecessor and H. heidelbergensis.
Neanderthals & Denisovans
Homo heidelbergensis is thought to have evolved into European Neanderthals around 200,000 years ago. You’ve probably heard of Neanderthals before. They get a lot of media attention since they were the closest species to us, coexisting with early Homo sapiens. They were around as recent as 35,000 years ago and are theorized to have been bred out of existence by us, the modern humans. Some people even have Neanderthal DNA in them!
As is to be expected, they engaged in a lot of the behaviors that contributed to our success as modern humans. They made adhesive from tree bark, built structures, made clothing, tried their hairy hands at seafaring, weaved baskets, used herbs, and discovered the joys of smoked food. They were likely the first of the Homo genus (classified as H. neanderthalensis) that could be described as apex predators.
A lot of the same can be said for the Denisovans too, though they’re more obscure with the laymen crowd. Neanderthals interbred with the Denisovans, blurring the lines between them for our paleoanthropologists. The Denisovans likely split from a common ancestor of the Neanderthals 400,000 years ago and evidence of them dried up 30,000 years ago. While Neanderthals thrived in central Europe, the Denisovans migrated throughout Siberia and the rest of Asia.
Europeans are more likely to have Neanderthal DNA while Denisovan DNA is present in Polynesians and the aboriginal peoples of other Pacific island nations. Through interbreeding with both, it is thought that H. sapiens acquired the genes necessary to brave the hardy mountainous regions of Europe and the humid, tropical environments of southern and east Asia.
Homo Sapiens
We are also theorized to have come from the heidelbergensis, so we evolved alongside the Neanderthals and the Denisovans. Carrying many of the skills that Neanderthals were also capable of, we migrated east and interbred with both of them. It’s likely we also clashed and outcompeted them at hunting and battle in some instances, and diseases/climate issues probably contributed to their decline while humanity weathered the storm.
As we mentioned already, we migrated across the Bering Strait land bridge. This makes us officially the first of the Homo genus to cross from the Old World to the New World, settling most of the globe.
From there, societies developed relatively independently of one another, from the first kingdoms in the Mesopotamian Cradle of Civilization to the early societies of modern-day China, Mexico, and Peru.
That’s where the human evolutionary journey seems to end, for now, as the subject matter moves from paleoanthropology to the study of ancient history instead. You know the story from there. Civilizations developed further and further until we have the interconnected, technologically advanced societies of today, and the ability to unearth our fascinating evolutionary story.
To finish this section, here’s a recap of the agreed-upon evolutionary path of mankind:
- Homo habilis – 2.4 MYA to 1.6 MYA
- Homo erectus – 1.8 MYA to 100,000 YA
- Homo heidelbergensis – 800,000 YA to 200,000 YA
- Neanderthals – 200,000 YA to 35,000 YA
- Denisovans – 400,000 YA to 40,000 YA
- Homo sapiens – 300,000 YA to present
Naturally, all figures are generalized and based on currently available fossils. There is a lot of room for error when trying to determine the origin and extinction dates of species.
Human Evolution Timeline
So, we’ve covered the end of the human evolutionary journey in the detail that it demands. That’s right, the Homo genus and even the Australopithecus are just the tip of the iceberg when it comes to the complete evolutionary past of mankind, covering only 2 million years. If you’re looking at the totality of human evolution, you can go beyond primates and explore 55 million years of progress to where we are today.
That’s exactly what we’ve done in the timeline below.
55+ Million Years Ago
Before the 55 million year mark, life had started as single-celled organisms 4.1 billion years ago, rudimentary animals developed 700 million years ago, vertebrates appeared 505 million years ago, tetrapods developed 390 million years ago and made the journey onto land. Then mammals formed 256 million years ago and split into primates anywhere from 85 to 66 million years ago.
Many of the early specimens were small, only went out at night, and ate insects. These were the Euarchonta, which then split into lemurs, tree shrews, and you guessed it, primates as we know them today. The early resemblances can be seen with Plesiadapiformes, believed to be the ancestor species of all primates today, including us.
For context, these beings appeared not long after the meteor. Yes, that meteor, though it should be said that it was likely the Chicxulub impact along with other factors that killed off the dinosaurs. Fortunately, that was just before our ancestors appeared.
With the stage set, we then see the order of primates separate into several suborders. First, the distinction was drawn between dry and wet-nosed primates with the Haplorhini and Strepsirrhini. That second group later became modern lemurs and lorises while the Haplorhini became simian monkeys, establishing the infraorder of Simiiformes. It was the Haplorhini where dependence on vitamin C was cultivated after the metabolism stopped producing it independently.
Simiiformes later split into the infraorders Platyrrhini and Catarrhini approximately 30 million years ago. By now it’s clear that we’re dealing with small monkeys with recognizably primate faces. Those Catarrhini then split into the Old World Monkeys and the apes, otherwise known as the Hominoidea. It’s here where trichromatic color develops in their eyesight.
25 million years ago, the Proconsul emerged as an early genus of these small primates. Their member species P. africanus may be an ancestor of all apes, including ourselves. As the millions of years roll on, we see the arrival of the Hominidae speciate from the gibbon. This gives rise to the Homininae, which speciated from the orangutan.
At 12 million years ago, the first discovered early great ape Danuvius guggenmosi. From their skeletal structure, they could likely hang from trees and walk with two legs, an early example of bipedalism.
8 – 6 MYA
While it took so long to develop small tree-dwelling monkeys and other related animals like lemurs and lorises, gorillas evolved 4 million years later, between 8 and 6 million years ago. Through the development of the Homininae comes the Hominini, whose member species both shared larynxes that repositioned over time. This led to a split between what we now know as early humans and chimpanzees. The first direct human ancestor that walked on two legs seems to be the Orrorin tugenensis.
5.5 – 5.8 MYA
As the proto-humans develop, we see the emergence of the Ardipithecus – “ground ape” – an early example of the early Hominina subtribe. If all these similar words are confusing – Hominidae, Homininae, Hominini, Hominina, etc., all you need to know is that the Hominina subtribe is also called Australopithecina. That’s similar to a term we’ve used several times already to categorize the last apes, the Australopithecines, that then gave rise to the Homo genus. The Ardipithecus, as you’ll see, evolved into the Australopithecus, hence the similarity in their nomenclature.
3.2 – 4 MYA
It wasn’t till about a million years later, approximately 4 million years ago, where our old friends the Australopithecus appear. We’re getting into familiar territory now. These were our first human ancestors to dwell on the African savanna, where many of our later ancestors would develop before venturing across the world.
3.2 million years ago, the Australopithecus afarensis we’ve named Lucy lived in what would become modern-day Ethiopia.
2.5 – 2.7 MYA
Another member of the Australopithecina group, the Paranthropus, developed in the woods and grasslands of Africa. They were too specialized as forest-dwelling herbivores, eventually dying out approximately 1.2 million years ago. They likely lived alongside Australopithecus africanus, Homo habilis, and Homo erectus.
By now, our ancestor species running around have lost most of their body hair to support endurance running, which meant they needed to sweat to regulate body heat. This exposed their skin more to the sun, so their skin would have been darker to avoid burning. As we know, the first of these was the H. habilis.
The development of stone tools brings the end of the Pliocene Epoch, which covered the period from 5.3 million years ago to 2.5 million years ago. Now we enter the Lower Paleolithic, the earliest part of the Stone Age which coincided with apes becoming early humans.
2 – 1.8 MYA
It wasn’t until a few hundred thousand years later that evidence of Homo erectus was found in Asia. These were the first hunter-gatherers, hence why they migrated far from Africa and in large numbers.
1.6 MYA – 600,000 YA
The presence of discolored sediments and charred wood is found in Koobi Fora, Kenya, and pre-civilization Israel. These discoveries are what led to the theory that the Homo erectus were the first fire-bearing human ancestors, which further allowed them to traverse the world.
Approximately 600,000 years ago, the Homo heidelbergensis lived in both Africa and Europe. Of all the ancestors, they had the most similar brain capacity to humans, suggesting natural selection towards intellect and that the heidelbergensis is a common ancestor of the Neanderthals and us, the Homo sapiens.
500,000 – 400,000 YA
Wooden huts near modern-day Chichibu, Japan, were found and dated to 500,000 years ago. While there have been stone structures and cave dwellings previously, this is one of the earliest examples of purpose-built shelters.
Around 400,000 years ago is where early humans began to hunt with spears. The ever-ingenious Homo heidelbergensis likely pioneered the weapon. This is when the common ancestor of the Neanderthals and the Denisovans likely split off from one another.
325,000 – 280,000 YA
Stoneworking becomes much more sophisticated now as we enter the Middle Paleolithic, with evidence of grinding stones and stone blades being found. We also have old footprints from early humans.
230,000 – 195,000 YA
This is where the Neanderthals appear and dominate Europe, from modern-day Britain to the Middle East. Benefiting from the fitness and the smarts of the H. erectus and the H. heidelbergensis, they were effective hunters and strategically co-operated with one another.
195,000 years ago, the Homo sapiens arrived and migrated across Europe and Asia. They live, fight, and breed with the Neanderthals and Denisovans present in both continents.
170,000 – 150,000 YA
It was 170,000 years ago that the Mitochondrial Eve may have been living in Africa. She is the direct matrilineal ancestor to all people living today. Humans were possibly capable of speech at this point and old jewelry also contained signs that they understood and expressed symbolism.
140,000 – 110,000 YA
The social and economic development of Homo sapiens continues with the earliest evidence of long-distance trade and decorative beads made from ostrich eggshells.
50,000 – 18,000 YA
The Middle Paleolithic comes to an end, bringing in the Upper Paleolithic. With this, human cultural development speeds up. Ritualistic burial begins and clothes become commonplace in society. Traps have been found, suggesting the ability to recognize movement patterns in animals and place traps to hunt instead of expending so much energy.
- sapiens finds their way to Australia. Elsewhere, cave art is found in France. In Asia, H. erectus finally dies out after the longest run out of all human ancestors. 18,000 years ago, the Indonesian offshoot H. floresiensis lived. They are nicknamed Hobbits because they were barely a meter tall.
12,000 – 5,000 YA
The Americas are finally populated by modern humans. Domestication of dogs is predicted to have occurred around 10,000 years ago and agriculture spreads across human society, forming the first villages.
This is where the Stone Age officially ends and the Bronze Age begins. Modern humans smelt simple metals like tin and copper, using them to replace the stone tools of our ancestors. The earliest known writing was also found 5,000 years ago.
4,000 – 3,500 BC
In the cradle of Mesopotamia, the Sumerians created the world’s first civilization. Others would later follow in Asia and South America.
Are Humans Still Evolving Today?
When people learn about evolution, it’s common to stop and think – are we still evolving today? It can be difficult to tell. Evolution, as Darwin originally laid it out, is supposed to be a very slow process of trial and error that takes many thousands of years before the slightest changes occur.
Some paleontologists believe that human evolution has slowed down or even stopped, like Stephen J. Gould. He posited that evolution operates by punctuated equilibrium, which just means that the Darwinian evolutionary process happens in short bursts and then plateaus for a period of stability, where no noticeable changes occur. Like any scientific theory, we don’t know for certain if that is the case.
If humans are still evolving, we live in a tiny, tiny moment in what is a long process, so we likely wouldn’t be able to tell. The best we can do is look at the human remains from 50,000 years ago, which haven’t changed and inspired Gould in 2000 to declare that humans have slowed or stopped biological changes.
Famous broadcaster Sir David Attenborough agreed, positing that birth control curbed the natural selection process. This gives rise to artificial selection, where offspring are consciously chosen. We may even take the artificial selection process to its logical endpoint with so-called designer babies. The offspring will instead mainly inherit cultural and technological traditions and habits from their parents. That’s essentially the theory of memetics as we know it today, where Darwinian evolutionary theory is applied to cultural ideas instead of biological genes.
Of course, the claim that evolution has slowed or stopped has its challenges. American geneticist Alan R. Templeton argued against Attenborough’s theory by asserting that our cultural and technological developments happen alongside and even inform our environment, so if anything, it’d help natural selection.
One example Templeton gives is that air travel has allowed the human gene pool to mix globally, stabilizing many populations’ health and creating fewer differences between us all. More traditionally, some are of the thought that webbed toes in humans are an adaptation toward semi-aquatic life, possibly due to climate concerns driven by human civilizations.
Others, like anthropologists Henry Harpending and Gregory Cochran, have claimed that human evolution has sped up in the last 10,000 years. They used data points involving lactose tolerance and cited one of the longest-running experiments in the world – the Framingham Heart Study.
In case you couldn’t tell yet, the answer is a big “maybe.” As time marches on, there’s no doubt that these competing theories will be proven right or wrong, or maybe replaced by new ones entirely, kind of like evolution itself.
Summary
With that, we come to the end of our guide on human evolution. We’ve discussed how evolution takes place for everybody, how the earliest men lived, how they evolved to become the smart beings that we are today, and whether we are still evolving right now. Our timeline summarizing over 55 million years of evolution also helped to conceptualize the scale and intricacy of evolution.
Now that you know how we evolved and the many debates that are still raging in the field of paleontology, you hopefully have a newfound appreciation for how complex nature can be. It took millions of years of trial and error to create us, so there’s no telling where humanity will go in the next thousands of years.