How many early human species existed on Earth?
It depends on your definition of human.
"We have one human species right now, and historically, that's really weird," said Nick Longrich, an evolutionary biologist at the University of Bath in the United Kingdom. "Not that far back, we weren't that special, but now we're the only ones left."
So, how many early human species were there?
When it comes to figuring out exactly how many distinct species of humans existed, it gets complicated pretty quickly, especially because researchers keep unearthing new fossils that end up being totally separate and previously unknown species.
"The number is mounting, and it'll vary depending on whom you talk to," said John Stewart, an evolutionary paleoecologist at Bournemouth University in the United Kingdom. Some researchers argue that the species known as Homo erectus is in fact made up of several different species, including Homo georgicus and Homo ergaster.
"It's all about the definition of a species and the degree to which you accept variation within a species," Stewart told Live Science. "It can become a slightly irritating and pedantic discussion, because everyone wants an answer. But the truth is that it really does depend."
What is a species?
The definition of a species used to be nice and simple: If two individuals could produce fertile offspring, they were from the same species. For example, a horseand a donkey can mate to produce a mule, but mules can't successfully reproduce with each other. Therefore, horses and donkeys, though biologically similar, are not the same species. In recent decades, however, that simplicity has given way to a more complex scientific debate about how to define a species. Critics of the interbreeding definition point out that not all life reproduces sexually; some plants and bacteria can reproduce asexually.
Others have argued that we should define species by grouping together organisms with similar anatomical features, but that method has weaknesses as well. There can be significant morphological variation between the sexes and even individuals of the same species in different parts of the world, making it a very subjective way of classifying life.
Some biologists prefer to use DNA to draw the lines between species, and with advancing technology, they can do so with increasing precision. But we don't have the DNA of every ancient human — the genome of Homo erectus, for instance, has never been sequenced, Live Science previously reported.
"Some people will tell you that Neanderthals are the same species as us," Stewart said. "They’re just a slightly different type of modern humans and the interbreeding is the proof, but again the definition of species has moved on from just interbreeding."
After taking all of this into account, some experts have argued that the concept of a species doesn't actually exist. But others say that, while a cast-iron definition of a species is almost impossible to achieve, it's still worth the effort so that we can talk about evolution — including the evolution of our own species — in a meaningful way.
So we muddle on, knowing that a species means different things to different people — which means, of course, that people will disagree on how many species of human have ever existed. It's also a question of what constitutes a human. To answer this question, it helps to understand the word hominin, a large group that includes humans and chimps going back to their shared ancestor.
"The chimpanzee and us have evolved from a common ancestor," Stewart said. If we decide that humans are everything that arrived after our split from ancient chimpanzees about 6 million to 7 million years ago, then it's likely to be a diverse group. The Smithsonian National Museum of Natural History has listed at least 21 human species that are recognized by most scientists. Granted, it's not a totally complete list; the Denisovans, for instance, are missing.
Those on the list include Homo sapiens, Neanderthals, the Indonesian hobbit-size people, Homo erectus and Homo naledi. The list also includes other species that existed closer in time to the common ancestor of humans and chimps, and so look more like chimpanzees than modern-day humans. Despite their looks, these species are still known as early humans. "You can't go back 5 million years and expect them to look like us," Stewart said.
If the Smithsonian says there are 21, then you can be sure the diversity is much greater, Stewart said. That’s because the list errs on the side of caution, picking the species that are close to universally recognized. For instance, the recently discovered dwarf human species Homo luzonensis, who is known from just a few bones from a cave in the Philippines, is not included on the Smithsonian's list.
Researchers also suspect there are many other fossilized species yet to be excavated. "The list has only ever grown and I don’t see why that will change," Stewart said.
Editor's Note: This article was updated at 9:49 a.m. EST on Jan. 25 to note that the remains of Homo luzonensis were found in the Philippines, not in Indonesia.
Originally published on Live Science.
https://www.livescience.com/how-many-human-species.html
Who these relatives were, and how they lived, is the subject of the next part of the gallery.
Apart from our species, the gallery features eight other kinds of human: Homo habilis, Homo rudolfensis, Homo erectus, Homo antecessor, Homo heidelbergensis, Homo floresiensis (nicknamed 'the Hobbit'), Homo neanderthalensis (the Neanderthals) and the recently discovered Homo naledi. The mysterious Denisovans, who may or may not turn out to be a distinct species, also make an appearance.
Scientifically accurate Homo neanderthalensis model by Kennis & Kennis. Neanderthals survived in Europe until the species went extinct about 39,000 years ago.
Homo sapiens – modern humans
Homo sapiens background
Homo sapiens age
300,000 years ago to present:
- archaic Homo sapiens from 300,000 years ago
- modern Homo sapiens from about 160,000 years ago
What the name Homo sapiens means
The name we selected for ourselves means ‘wise human’. Homo is the Latin word for ‘human’ or ‘man’ and sapiens is derived from a Latin word that means ‘wise’ or ‘astute’.
Other Homo sapiens names
Various names have been used for our species including:
- ‘Cro-Magnon Man’ is commonly used for the modern humans that inhabited Europe from about 40,000 to 10,000 years ago.
- The term ‘archaic’ Homo sapiens has sometimes been used for African fossils dated between 300,000 and 150,000 years of age that are difficult to classify due to a mixture of modern and archaic features. Some scientists prefer to place these fossils in a separate species, Homo helmei.
- Homo sapiens sapiens is the name given to our species if we are considered a sub-species of a larger group. This name is used by those that describe the specimen from Herto, Ethiopia as Homo sapiens idàltu or by those who believed that modern humans and the Neanderthals were members of the same species. (The Neanderthals were called Homo sapiens neanderthalensis in this scheme).
Major fossil sites of early Homo sapiens
Fossils of the earliest members of our species, archaic Homo sapiens, have all been found in Africa. Fossils of modern Homo sapiens have been found in Africa and in many other sites across much of the world. Sites older than 150k include Florisbad, Omo-Kibish, Ngaloba and Herto. Sites dating to about 100k include Klasies River Mouth, Border Cave, Skhul and Qafzeh. Sites younger than 40k include Dolni Vestonice, Cro-Magnon, Aurignac and Lake Mungo.
Homo sapiens Relationships with other species
Homo sapiens evolved in Africa from Homo heidelbergensis. They co-existed for a long time in Europe and the Middle East with the Neanderthals, and possibly with Homo erectus in Asia and Homo floresiensis in Indonesia, but are now the only surviving human species.
For information on modern humans interbreeding with other human species see:
The transition to modern humans
African fossils provide the best evidence for the evolutionary transition from Homo heidelbergensis to archaic Homo sapiens and then to early modern Homo sapiens. There is, however, some difficulty in placing many of the transitional specimens into a particular species because they have a mixture of intermediate features which are especially apparent in the sizes and shapes of the forehead, brow ridge and face. Some suggest the name Homo helmei for these intermediate specimens that represent populations on the brink of becoming modern. Late surviving populations of archaic Homo sapiens and Homo heidelbergensis lived alongside early modern Homo sapiens before disappearing from the fossil record by about 100,000 years ago. Key specimens that reveal an evolutionary transition from archaic to modern Homo sapiens include Florisbad cranium, LH18 from Laetoli, Omo 1 and 2 from Omo-Kibish, Herto skull from Ethiopia and Skhul 5 from Israel.
Important specimens: Late early modern Homo sapiens
- Liujiang – a skull discovered in 1958 in Guanxi province, South China. Age is uncertain, but at least 15,000 years old. This skull lacks the typically northern Asian features found in modern populations from those regions, lending support to popular theories that such features only arose in the last 8000 years.
- Aurignac – skull discovered in Aurignac, France. The first Aurignac fossils were accidentally found in 1852. A workman digging a trench in a hillside found a cave that had been blocked by rock but after clearing away the debris he found 17 skeletons. The skeletons were taken to a local cemetery for burial but later investigations indicated that the skeletons were actually up to 10,000 years old.
- Cro-Magnon 1 – a 32,000-year-old skull discovered in 1868 in Cro-Magnon rockshelter, Les Eyzies, France. This adult male represents the oldest known skull of a modern human from western Europe. Cro-Magnon skeletons have proportions similar to those of modern Africans rather than modern Europeans. This suggests that the Cro-Magnons had migrated from a warmer climate and had a relatively recent African ancestry.
Important specimens: Early modern Homo sapiens
- Herto – a 160,000-year-old partial skull discovered in1997 in Herto, Ethiopia. This skull from an adult male and those of another adult and a child were found in 1997 and publicly announced in 2003. They are some of the oldest fossils of modern Homo sapiens yet discovered. Some scientists regard these fossils as a sub-species of modern humans (named Homo sapiens idàltu) because of some slight differences in their skull features. They show a suite of modern human traits, mixed with archaic and early modern features. Also of significance are cut marks on the child's skull. These were made when the bone was still fresh in a manner indicating ritual practice. The skull also appeared 'polished' from repeated handling before it was laid in the ground.
- Omo 1 – a partial skull discovered in1967 in Omo-Kibish, Ethiopia. A recently published date for this skull was about 195,000 years old, but this is disputed. However, it is still one of the oldest known fossils of early modern Homo sapiens. Features which show the transition from an archaic to an early modern Homo sapiens include a more rounded and expanded braincase and a high forehead. Now dated to the same age as Omo 2, it does raise interesting questions about why it appears to have slightly more advanced features than Omo 2. Were they from the same population?
- Skhul 5 – a 90,000-year-old skull discovered in1932 in Skhul Cave, Mount Carmel, Israel. This skull of an adult male has developed relatively modern features including a higher forehead although it still retains some archaic features including a brow ridge and slightly projecting face. This specimen and others from the Middle East are the oldest known traces of modern humans outside of Africa. They prove that Homo sapienshad started to spread out of Africa by 100,000 years ago, although it may be that these remains represent a population that did not expand beyond this region – with migrations to the rest of the world occurring later, about 60-70,000 years ago.
Important specimens: Archaic Homo sapiens
- LH 18 – skull discovered in 1976 in Ngaloba, Laetoli, Tanzania. Age is about 120,000 years old (but debated). This skull is transitional between Homo heidelbergensis and early modern Homo sapiens. It has a number of primitive features but also has some modern characteristics such as a reduced brow ridge and smaller facial features. The late date of this specimen indicates that archaic humans lived alongside modern populations for some time.
- Florisbad – a 260,000-year-old partial cranium discovered in 1932 in Florisbad, South Africa. This skull shows features intermediate between Homo heidelbergensis and early modern Homo sapiens. The face is broad and massive but still relatively flat and the forehead is approaching the modern form.
- Omo 2 – a 195,000-year-old braincase discovered in 1967 in Omo-Kibish, Ethiopia. Like LH 18, this braincase shows a blend of primitive and modern features that places it as a member of a population transitional between Homo heidelbergensis and early modern Homo sapiens. Its primitive features include a heavier, more robust construction; an angled rather than rounded rear section; and a lower, sloping forehead. Refer to Omo 1 specimen for interesting comparisons.
Homo sapiens key physical features
Homo sapiens skulls have a distinctive shape that differentiates them from earlier human species. Their body shape tends to vary, however, due to adaptation to a wide range of environments.
Homo sapiens Body size and shape
- the earliest Homo sapiens had bodies with short, slender trunks and long limbs. These body proportions are an adaptation for surviving in tropical regions due to the greater proportion of skin surface available for cooling the body. More stocky builds gradually evolved when populations spread to cooler regions, as an adaptation that helped the body retain heat.
- Modern humans now have an average height of about 160 centimetres in females and 175 centimetres in males.
Brain
- Homo sapiens living today have an average brain size of about 1350 cubic centimetres which makes-up 2.2% of our body weight. Early Homo sapiens, however, had slightly larger brains at nearly 1500 cubic centimetres.
Skull
- modern Homo sapiens skulls have a short base and a high braincase. Unlike other species of Homo, the skull is broadest at the top. The fuller braincase also results in almost no post-orbital constriction or narrowing behind the eye sockets
- back of the skull is rounded and indicates a reduction in neck muscles
- face is reasonably small with a projecting nose bone
- brow ridge is limited and the forehead is tall
- orbits (eye sockets) are square rather than round
Jaws and teeth
- jaws are short which result in an almost vertical face
- usually no gap (retromolar space) between the last molar teeth and the jaw bone
- jaws are lightly built and have a protruding bony chin for added strength. Homo sapiens is the only species to have a protruding chin.
- shortened jaw has affected the arrangement of the teeth within the jaw. They are now arranged in a parabolic shape in which the side rows of teeth splay outwards rather than remain parallel as in our earliest long jawed ancestors.
- teeth are relatively small compared with earlier species. This is especially noticeable in the front incisor and canine teeth.
- front premolar teeth in the lower jaw have two equal-sized cusps (bumps on the chewing surface)
Limbs and pelvis
- limb bones are thinner and less robust than earlier human species and indicate a reduction in muscle size from earlier humans.
- legs are relatively long compared with the arms.
- finger and toe bones are straight and without the curvature typical of our earliest australopithecine ancestors.
- pelvis is narrower from side-to-side and has a deeper bowl-shape from front-to-back than previous human species.
Homo sapiens Lifestyle
Homo sapiens Culture and technology
The earliest Homo sapiens had a relatively simple culture, although it was more advanced than any previous species. Rare evidence for symbolic behaviour appears at a number of African sites about 100,000 years ago, but these artistic expressions appear more of a flicker of creativity than a sustained expression. It is not until about 40,000 years ago that complex and highly innovative cultures appear and include behaviour that we would recognise as typical of modern humans today.
Many researchers believe this explosion of artistic material in the archaeological record about 40,000 years ago is due to a change in human cognition - perhaps humans developed a greater ability to think and communicate symbolically or memorise better. However, as there are obvious attempts at art before this, perhaps there are other reasons. One theory is that population size and structure play a key role as social learning is considered more beneficial to developing complex culture than individual innovations are. Bigger populations often accumulate more cultural attributes than isolated groups.
Homo sapiens Tools
Initially, Homo sapiens made stone tools such as flakes, scrapers and points that were similar in design to those made by the Neanderthals (Homo neanderthalensis). This technology appeared about 250,000 years ago, coinciding with the probable first appearance of early Homo sapiens. It required an ability for abstract thought to mentally plan a series of steps that could then be executed. Only a small number of tools were produced from each core (the original stone selected for shaping) but the tools produced by this prepared-core method maximised the cutting edge available. Historically, archaeologists used different terminologies for Lower Palaeolithic cultures in different parts of the world. Many of these terms are now consolidated within the Mode 3 technology to emphasise the similarities between these technologies.
As more sophisticated techniques developed in some parts of the world, this early Mode 3 technology was replaced by either Mode 4 or Mode 5 technology and the use of a wider range of materials including bone, ivory and antler. Mode 4 technology first appeared in Africa about 100,000 years ago. It is characterised by the production of long, thin stone flakes that were shaped into long blade knives, spearheads and other tools. Mode 5 technology specialised in the production of very small blades (microliths) that were often used in composite tools having several parts. These tools included small-headed arrows, barbed spears and sickles. Regional variation in these tool cultures developed with an influx of new styles and techniques especially within the last 40,000 years, including the Magdalenian and Aurignacian.
Homo sapiens use of Fire
Sophisticated control of fire, including complex hearths, pits and kilns, allowed Homo sapiens to survive in regions that even the cold-adapted Neanderthals had been unable to inhabit.
The Cro-Magnon site at Dolni Vestonice in the Czech Republic produced the earliest evidence for high temperature kilns and ceramic technology. The kilns, dated at 26,000 years old, were capable of firing clay figurines at temperatures over 400 degrees Celsius. About 2000 fired lumps of clay were found scattered around the kiln.
Homo sapiens Clothing and personal adornment
Animal hide clothing may have been worn in cooler areas, although direct evidence of clothing only exists for the last 30,000 years. This evidence includes specialised tools such as needles; adornments such as buttons and beads sewn onto clothing; and the remains of animals, such as arctic foxes and wolves, that indicate they were trapped for their fur. Clothes that were sewn provided better protection from the cold than clothes that were merely tied together.
Fibres from flax plants were discovered in a cave in Georgia in 2009, dating to about 36,000 years old. The flax was most likely used to make clothes and woven baskets, and a small number appear to be dyed. They are the oldest example of their kind ever found. Textile impressions have been discovered at other European sites have, but no actual remains.
Items of personal adornment not sewn onto clothing include ivory, shell, amber, bone and tooth beads and pendants. Ostrich eggshell beads that date from about 45,000 years ago have been found in Africa, as well as pierced shell beads in Morocco dating to 80,000 years ago and marine shell beads from Israel dating to 90,000 years old, but body adornment only become prolific from about 35,000 years ago.
One of the earliest known pendants is a horse carved in mammoth ivory from Vogelherd, Germany. It is dated at 32,000 years old. Body adornments like this are evidence that humans had progressed from merely trying to survive and were now concerned with their appearance.
Homo sapiens Art
Cave art began to be produced about 40,000 years ago in Europe and Australia. Most of the art depicts animals or probable spiritual beings, but smaller marks in many caves in France, and possibly others in Europe, are now being analysed as they may be a written 'code' familiar to many prehistoric tribes. In particular, 26 symbols appear over and over again across thousand of years, some of them in pairs and groups in what could be a rudimentary 'language'. These suggest that early Europeans were attempting to represent ideas symbolically rather than realistically and share information acorss generations. The oldest of these symbols date to about 30,000 years old.
Evidence of musical instruments first appeared about 32,000 years ago in Europe. Palaeolithic bone flutes and whistles from various sites in France range in age from 30,000 to 10,000 years old.
Portable artwork, such as carved statuettes, first appeared about 35-40,000 years ago in Europe. Venus figurines were widespread in Europe by 28,000 years ago. Fragments from Germany found in 2009, suggest their origins started at least 35,000 years ago. An ivory female head with bun from Dolni Vestonice, Czech Republic, is one of only 2 human head carvings from this period that show eye sockets, eyelids and eyeballs. It is dated at 26,000 years old.
Red ochre pieces from Blombos Cave in South Africa, dating to about 100-80,000 years ago, show evidence of engraving that may be an expression of art or simply incidental marking made during other activities. However, other signs of possible symbolic behaviour, including shell beads and sophisticated tools (known as Still Bay points) have also come from this site, strengthening the case for early artistic expression.
Homo sapiens Settlement
Early Homo sapiens often inhabited caves or rock shelters if these were available. More recently, especially within the last 20,000 years, natural shelters were enhanced with walls or other simple modifications. In open areas, shelters were constructed using a range of framework materials including wooden poles and the bones of large animals, such as mammoths. These structures were probably covered with animal hides and the living areas included fire hearths.
Living sites were much larger than those occupied by earlier humans and a comparison with modern traditional peoples suggests that clans consisted of between 25 and 100 members.
Burial
Burials were infrequent and very simple prior to 40,000 years ago and then began to become more elaborate with the inclusion of valued objects such as tools and body adornments. Red ochre was sprinkled over many of the bodies prior to burial.
One of the earliest deliberate burials of a modern human comes from Jebel Qafzeh in Israel. Dating to 90,000 years old, the grave contains the bones of a young woman buried with a young child at her feet. An additional 21 skeletons were found in the same cave.
Environment and diet
Early modern humans were adapted to life in the tropics but by 40,000 years ago they occupied a range of environments across the continents of Africa, Europe, Asia and Australia. Within the last 20,000 years humans have also spread into the Americas. Today, our culture and technology allows us to live in most environments on our planet as well as some off our planet.
All Homo sapiens were once hunter-gatherers living on wild plants and animals. It was only about 11,000 years ago that humans began to domesticate plants and animals although wild foods still remained important in the diet. Our species has a wide-ranging and essentially omnivorous diet. This has enabled us to utilise the food resources found in the wide variety of environments we inhabit.
https://australian.museum/learn/science/human-evolution/how-do-we-know-how-they-behaved/
