Our Ancestors and how we got from then to now

The following text caught my attention^[1]:

‘The authors present comprehensive qualitative and quantitative analyses of fossilised remains from a site in Israel dated to 140,000 to 120,000 years ago, indicating the presence of a previously unrecognised group of hominins representing the last surviving populations of Middle Pleistocene Homo in Europe, southwest Asia, and Africa.’

The text above comes from a paper co-authored by two members of the Recanati Institute in Israel (Prof. Ruth Shahack-Gross and Dr David Friesem), which was published in the prestigious journal Science^[2] and a report on it appeared on the  BBC News website^[3].

Because it looked interesting, I did some research to find out as much as possible and prepared a short excerpt, which is given below.

Timeline of Human Evolution
Human evolution is the process by which human beings developed on Earth from now-extinct primates.

The Smithsonian Institute summarise Human Evolution^[4] as:

“Human evolution is the lengthy process of change by which people originated from ape-like ancestors. Scientific evidence shows that the physical and behavioural traits shared by all people originated from ape-like ancestors and evolved over a period of approximately six million years.

“One of the earliest defining human traits, bipedalism — the ability to walk on two legs — evolved over 4 million years ago. Other important human characteristics — such as a large and complex brain, the ability to make and use tools, and the capacity for language — developed more recently. Many advanced traits — including complex symbolic expression, art, and elaborate cultural diversity — emerged mainly during the past 100,000 years.

“Humans are primates. Physical and genetic similarities show that the modern human species, Homo sapiens, has a very close relationship to another group of primate species, the apes. Humans and the great apes (large apes) of Africa — chimpanzees (including bonobos, or so-called “pygmy chimpanzees”) and gorillas — share a common ancestor that lived between 8 and 6 million years ago. Humans first evolved in Africa, and much of human evolution occurred on that continent. The fossils of early humans who lived between 6 and 2 million years ago come entirely from Africa.

“Most scientists currently recognise some 15 to 20 different species of early humans. Scientists do not all agree, however, about how these species are related or which ones simply died out. Many early human species — certainly the majority of them – left no living descendants. Scientists also debate over how to identify and classify particular species of early humans, and about what factors influenced the evolution and extinction of each species.

“Early humans first migrated out of Africa into Asia probably between 2 million and 1.8 million years ago. They entered Europe somewhat later, between 1.5 million and 1 million years. Species of modern humans populated many parts of the world much later. For instance, people first came to Australia probably within the past 60,000 years and to the Americas within the past 30,000 years or so. The beginnings of agriculture and the rise of the first civilisations occurred within the past 12,000 years.”

A key point in the timeline of human evolution is 195,000 years ago – that’s when our own species, Homo sapiens, appeared on the scene – and shortly after began to migrate across Asia and Europe. The oldest modern human remains are two skulls found in Ethiopia that date to this period. The average human brain volume was then 1350 cubic cm^[5].

Skulls of successive or near-successive human evolutionary ancestors, up until modern Homo sapiens.

(Mya – million years ago, kya – thousand years ago).

Picture Credit: © This file is licensed under the Creative Commons 
Attribution-Share Alike 4.0 International license.
URL: https://commons.wikimedia.org/wiki/File:Skull_evolution.png

The human species eventually developed a much larger brain than that of other primates—typically 1,330 cubic cm in modern humans, nearly three times the size of a chimpanzee or gorilla brain^[6]. After a period of stasis^[7] with Australopithecus anamensis and Ardipithecus, species with smaller brains due to their bipedal locomotion^[8], the pattern of encephalisation^[9] started with Homo habilis, whose 600 cubic cm brain was slightly larger than that of chimpanzees.

This evolution continued in Homo erectus with 800–1,100 cubic cm and reached a maximum in Neanderthals with 1,200–1,900 cubic cm (73–116 cu in), larger even than modern Homo sapiens. This brain increase manifested during postnatal brain growth, far exceeding that of other apes (heterochrony). It also allowed for extended periods of social learning and language acquisition in juvenile humans, beginning as long as 2 million years ago.

Furthermore, the changes in the structure of human brains may be even more significant than the increase in size^[10].

Changes along the way^[11]
Some surprising changes have occurred in the evolution of our species, including these:

Ulnar opposition
The ulnar opposition—the contact between the thumb and the tip of the little finger of the same hand—is unique to the genus Homo, including Neanderthals, the Sima de los Huesos hominins and anatomically modern humans. In other primates, the thumb is short and unable to touch the little finger. The ulnar opposition facilitates the precision grip and power grip of the human hand, underlying all the skilled manipulations.

Other changes
A number of other changes have also characterised the evolution of humans, among them an increased importance on vision rather than smell; a longer juvenile developmental period and higher infant dependency; a smaller gut; faster basal metabolism; loss of body hair; evolution of sweat glands; a change in the shape of the dental arcade from being u-shaped to being parabolic; development of a chin (found in Homo sapiens alone); development of styloid processes; and the development of a descended larynx.

Australopithecus africanus
This species was the first of our pre-human ancestors to be discovered but was initially rejected from our family tree because of its small brain. This opinion changed when new evidence showed this species had many features intermediate between apes and humans. This species lived between 3.2 and 2 million years ago.

Taung Child: A partial skull and brain endocast was discovered in 1924 in Taung, South Africa. The 2.3 million-year-old skull was of a young child and is the ‘type specimen’ or official representative of this species. It was the first fossil of a human ancestor ever found in Africa and was also the first to be classified in the genus Australopithecus.^[12]

Australopithecus africanus was anatomically similar to Australopithecus afarensis, combining human-like and ape-like features. Compared to afarensis, africanus had a rounder cranium housing a larger brain and smaller teeth, but it also had some ape-like features, including relatively long arms and a strongly sloping face jutting out from underneath the braincase with a pronounced jaw.  Like afarensis, the pelvis, femur (upper leg), and foot bones of africanus indicate that it walked bipedally, but its shoulder and hand bones suggest they were also adapted for climbing. It took more than 20 years for the scientific community to accept Australopithecus as a member of the human family tree^[13].

Homo habilis
One of the earliest members of the genus Homo, this species has a slightly larger braincase and smaller face and teeth than in Australopithecus or older hominin species. But it still retains some ape-like features, including long arms and a moderately-prognathic face. Its name, which comes from the Latin meaning ‘handy’ or ‘skilful’, was given in 1964 because this species was thought to represent the first maker of stone tools.  Currently, the oldest stone tools are dated slightly older than the oldest evidence of the genus Homo.^[14]

Homo erectus
Homo erectus is an extinct species of archaic human from the Pleistocene (often referred to as the ‘Ice Age’), with its earliest occurrence about 2 million years ago, and its specimens are among the first recognisable members of the genus Homo^[15].

The extinct ancient human Homo erectus is a species of firsts. It was the first of our relatives to have human-like body proportions, with shorter arms and longer legs relative to its torso. It was also the first known hominin to migrate out of Africa and possibly the first to cook food. In terms of species survival, fossil evidence for Homo erectus stretches over more than 1.5 million years, making it by far the longest surviving of all our human relatives^[16].

Homo ergaster
Homo ergaster is an extinct species or subspecies of archaic humans who lived in eastern and southern Africa in the Early Pleistocene. Whether Homo ergaster constitutes a species of its own or should be subsumed into Homo erectus is an ongoing and unresolved dispute within palaeoanthropology^[17].

Homo ergaster, meaning ‘workman’ due to its advanced lithic (stone) technology, is also referred to as African Homo erectus. The most complete skeleton was discovered at Lake Turkana, Kenya, in 1984 by Kayoma Kimeu and Alan Walker, who nicknamed the 1.6 million-year-old specimen ‘Turkana Boy’^[18].

Homo ergaster was the first of our ancestors to look like modern humans. These people were generally tall and slender and may also have been relatively hairless^[19].

Homo antecessor or Homo heidelbergensis
This species name is highly debated, with many experts considering the remains to be Homo heidelbergensis^[20]. Whatever species they come from, these fossils are the oldest Homo found in western Europe. The species name antecessor is a Latin word meaning ‘explorer’, ‘pioneer’ or ‘early settler’ and this name was assigned due to the belief that these people belonged to the first human population as yet known from the European continent^[21]. Homo antecessor, which first came to light in the 1990s, is known almost entirely from one cave in northern Spain’s Atapuerca Mountains^[22].

Homo Erectus and Homo Sapiens^[23]
Modern humans – that’s you and me (Homo sapiens), the species that we are, means ‘wise man’ in Latin. That, of course, includes women. Our species is the only surviving species of the genus Homo but where we came from has been a topic of much debate. Modern humans originated in Africa within the past 200,000 years and evolved from their most likely recent common ancestor, Homo erectus, which means ‘upright man’ in Latin. Homo erectus is an extinct species of human that lived between 1.9 million and 135,000 years ago.

Historically, two key models have been put forward to explain the evolution of Homo sapiens. These are often referred to as the ‘out of Africa’ model and the ‘multi-regional’ model. The ‘out of Africa’ model is currently the most widely accepted model. It proposes that Homo sapiens evolved in Africa before migrating across the world.

On the other hand, the ‘multi-regional’ model proposes that the evolution of Homo sapiens took place in several places over a long period. The intermingling of the various populations eventually led to the single Homo sapiens species of today.

Picture Credit: [Resized] “Neanderthal Man” by Michael Brace is licensed under CC BY-NC-ND 2.0

The Nesher Ramla Homo type
Researchers believe that the remains uncovered near to the city of Ramla (Israel) represent one of the “last survivors” of a very ancient human group. Details have been published in the journal Science Magazine^[24].

The archeological finds consist of a partial skull and jaw from an individual who lived between 120,000 and 140,000 years ago.

Research team members think the ‘ancient human’ descended from an earlier species that may have spread out of the region hundreds of thousands of years ago and given rise to Neanderthals in Europe and their equivalents in Asia.

The scientists named the newly discovered lineage the “Nesher Ramla Homo type”.

Skull, but no chin^[25]
Homo sapiens (that’s us) have tall, rounded skulls encasing our large brains, but the remains discovered by the researchers had features typical of older species of Homo that likely arrived in the Middle East around 450,000 years ago, a quarter of a million years before Homo sapiens showed up.

Meanwhile, teeth seemed very similar to those found in local hominin populations dated to 400,000 years ago, as well as those of the Neanderthals.

Researchers used the scant skull remains from the Nesher Ramla find to create a virtual reconstruction of a hominin who lived until relatively recently but has very archaic features, including the lack of a chin.

Homo Longi (aka ‘Dragon Man’)
As reported on BBC News^[26], Chinese researchers have unveiled an ancient skull that could belong to a completely new species of human. The research team has claimed it is our closest evolutionary relative among known species of ancient humans, such as Neanderthals and Homo erectus. The skull is much bigger than that of Homo sapiens and other human species – and its brain size is similar to that of our own species^[27].

Nicknamed “Dragon Man”, the specimen represents a human group that lived in East Asia at least 146,000 years ago. It was found at Harbin, north-east China, in 1933 but only came to the attention of scientists more recently. An analysis of the skull has been published in the journal The Innovation^[28].

One of the UK’s leading experts in human evolution, Prof Chris Stringer from London’s Natural History Museum, was a member of the research team. He told BBC News^[29]:

‘In terms of fossils in the last million years, this is one of the most important yet discovered…What you have here is a separate branch of humanity that is not on its way to becoming Homo sapiens (our species) but represents a long-separate lineage that evolved in the region for several hundred thousand years and eventually went extinct.’

Picture Credit: Shaanxi Provincial Museum, Xi’an, Western Zhou Gallery. Gary Todd https://www.flickr.com/photos/101561334@N08/9929912223/
This file is made available under the Creative Commons CC0 1.0 Universal Public Domain Dedication

The Harbin research team have generated a family tree (“phylogeny”) of human lineages to see how the species relates to modern humans. They discovered that five previously unidentified fossils from northeastern China are from Homo longi. It predicts that the common ancestor of Homo longi and Homo sapiens lived approximately 950,000 years ago.

The article on the DiscoverMagazine website suggests that longi and sapiens shared a common ancestor with Neanderthals over one million years ago, meaning we may have split from Neanderthals 400,000 years earlier than was previously thought^[30].

Homo Neanderthalensis^[31]
The Neanderthals lived in Eurasia up to 200,000 years ago, say Britannica.com^[32]. Their appearance was like ours, although they were shorter and stockier with angled cheekbones, prominent brow ridges and wide noses. Scientists say that the Neanderthals were smarter than they looked as they used tools, buried their dead and controlled fire, among other intelligent behaviours. Skeleton remains suggest that they took care of their sick and those who could not care for themselves.

Picture Credit: “Our Cousin -Neanderthal” by p_a_h is licensed under CC BY-NC-ND 2.0

Neanderthals typically lived to about 30 years old, although some lived longer. It is theorised that for a time, Neanderthals probably shared the Earth with other Homo species.^[33]

Neanderthals most likely became extinct due to assimilation into the modern human genome, great climatic change, disease, or a combination of these and other factors. Neanderthals lived alongside early modern humans for at least part of their existence.  Some encounters with homo sapiens were very intimate – some of us have inherited around two per cent Neanderthal DNA.

Facts about Neanderthals:

• Brain size: at least 1200 to 1750 cubic cm
• Height: about 1.50-1.75m
• Weight: about 64-82kg

The Denisovans or Denisova hominims

Picture Credit: “Denisovan Reconstruction C” by TheoJunior is licensed under CC BY-NC-SA 2.0

The Denisovans or Denisova hominins are an extinct species or subspecies of archaic humans that ranged across Asia during the Lower (the earliest subdivision of the Paleolithic or Old Stone Age) and Middle Paleolithic (the second subdivision of the Paleolithic or Old Stone Age as understood in Europe, Africa and Asia).

Denisovans are known from few remains: most of what is known about them comes from DNA evidence. Pending consensus on their taxonomic status, they have been referred to as Homo Denisova, altaiensis.

Denisovans apparently interbred with modern humans, with about 3–5% of the DNA of Melanesians and Aboriginal Australians and around 7–8% in Papuans deriving from Denisovans.

A female who died around 90,000 years ago was half Neanderthal and half Denisovan, according to genome analysis of a bone discovered in a Siberian cave. This is the first time scientists have identified an ancient individual whose parents belonged to distinct human groups. The findings were published on 22^nd August 2018 in Nature^[34]. It’s worth reading.

Sources and Further Reading

https://www.bbc.co.uk/news/science-environment-57586315

• https://science.sciencemag.org/cgi/doi/10.1126/science.abh3169
• https://science.sciencemag.org/content/372/6549/1424
• https://www.nationalgeographic.com/science/article/puzzling-skull-discovery-may-point-previously-unknown-human-ancestor
• https://www.bbc.co.uk/news/science-environment-57432104
• https://www.cell.com/the-innovation/fulltext/S2666-6758(21)00056-4
• https://www.nhm.ac.uk/discover/who-were-the-neanderthals.html
• https://www.britannica.com/topic/Neanderthal
• https://www.livescience.com/28036-neanderthals-facts-about-our-extinct-human-relatives.html
• https://biomed.brown.edu/Courses/BIO48/39.Human.Evolution.HTML
• https://www.britannica.com/science/human-evolution
• https://www.yourgenome.org/stories/evolution-of-modern-humans
• https://scienceget.net/evolution/archaeologists-make-dramatic-discovery-of-a-prehistoric-human-type/
• https://www.newscientist.com/article/dn9989-timeline-human-evolution/#ixzz7L4QpL3CW
• https://australian.museum/learn/science/human-evolution/homo-antecessor/
• https://www.discovermagazine.com/planet-earth/homo-longi-extinct-human-species-that-may-replace-neanderthals-as-our
• https://humanorigins.si.edu/education/introduction-human-evolution
• Videos: https://www.britannica.com/media/1/275670/227182
• https://en.wikipedia.org/wiki/Human_evolution
• https://en.wikipedia.org/wiki/Denisovan
• https://www.nature.com/articles/d41586-018-06004-0
• https://en.wikipedia.org/wiki/Homo_longi
• https://australian.museum/learn/science/human-evolution/australopithecus-africanus/
• https://humanorigins.si.edu/evidence/human-fossils/species/australopithecus-africanus
• https://en.wikipedia.org/wiki/Homo_habilis
• https://humanorigins.si.edu/evidence/human-fossils/species/homo-habilis
• https://australian.museum/learn/science/human-evolution/homo-habilis/
• https://en.wikipedia.org/wiki/Homo_erectus
• https://www.nhm.ac.uk/discover/homo-erectus-our-ancient-ancestor.html
• https://milnepublishing.geneseo.edu/the-history-of-our-tribe-hominini/chapter/homo-ergaster/
• https://en.wikipedia.org/wiki/Homo_ergaster
• https://www.bradshawfoundation.com/origins/homo_ergaster.php

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Picture Credit: “Human Evolution?” by bryanwright5@gmail.com is licensed under CC.

1. At: https://science.sciencemag.org/content/372/6549/1424 ↑
2. At: https://www.science.org/doi/full/10.1126/science.abh3020 ↑
3. At: https://www.bbc.co.uk/news/science-environment-57586315 ↑
4. At: https://humanorigins.si.edu/education/introduction-human-evolution ↑
5. Read more at:  https://www.newscientist.com/article/dn9989-timeline-human-evolution/#ixzz7L4p6GUPx ↑
6. Source: Schoenemann, P. Thomas (October 2006). “Evolution of the Size and Functional Areas of the Human Brain”. Annual Review of Anthropology. 35: 379–406. doi:10.1146/annurev.anthro.35.081705.123210. ISSN 0084-6570. S2CID 7611321. ↑
7. Stasis: a state or period of stability during which little or no evolutionary change in a lineage occurs. ↑
8. Source: Brown, Graham; Fairfax, Stephanie; Sarao, Nidhi. “Tree of Life Web Project: Human Evolution”. www.tolweb.org. ↑
9. See meaning at: https://www.definitions.net/definition/encephalization ↑
10. Sources:(1) Park MS, Nguyen AD, Aryan HE, U HS, Levy ML, Semendeferi K (March 2007). “Evolution of the human brain: changing brain size and the fossil record”. Neurosurgery. 60 (3): 555–562. doi:10.1227/01.NEU.0000249284.54137.32. ISSN 0148-396X. PMID 17327801. S2CID 19610624.(2) Bruner, Emiliano (December 2007). “Cranial shape and size variation in human evolution: structural and functional perspectives”. Child’s Nervous System. 23 (12): 1357–1365. CiteSeerX 10.1.1.391.288. doi:10.1007/s00381-007-0434-2. ISSN 0256-7040. PMID 17680251. S2CID 16163137.

    (3) Potts, Richard (October 2012). “Evolution and Environmental Change in Early Human Prehistory”. Annual Review of Anthropology. 41: 151–167. doi:10.1146/annurev-anthro-092611-145754. ISSN 0084-6570.

    (4) Leonard, William R.; Snodgrass, J. Josh; Robertson, Marcia L. (August 2007). “Effects of brain evolution on human nutrition and metabolism”. Annual Review of Nutrition. 27: 311–327. doi:10.1146/annurev.nutr.27.061406.093659. ISSN 0199-9885. PMID 17439362. S2CID 18869516. ↑

11. Source: https://en.wikipedia.org/wiki/Human_evolution ↑
12. Source: https://australian.museum/learn/science/human-evolution/australopithecus-africanus/ ↑
13. Source: https://humanorigins.si.edu/evidence/human-fossils/species/australopithecus-africanus ↑
14. Sources: https://en.wikipedia.org/wiki/Homo_habilis and https://humanorigins.si.edu/evidence/human-fossils/species/homo-habilis ↑
15. Source: https://en.wikipedia.org/wiki/Homo_erectus ↑
16. Source: https://www.nhm.ac.uk/discover/homo-erectus-our-ancient-ancestor.html ↑
17. Source: https://en.wikipedia.org/wiki/Homo_ergaster ↑
18. Source: https://www.bradshawfoundation.com/origins/homo_ergaster.php ↑
19. Source: https://australian.museum/learn/science/human-evolution/homo-ergaster/ ↑
20. Homo heidelbergensis is an extinct species or subspecies of archaic human which existed during the Middle Pleistocene. It was subsumed as a subspecies of Homo erectus in 1950 as Homo erectus heidelbergensis, but towards the end of the century, it was more widely classified as its own species. ↑
21. Source: https://australian.museum/learn/science/human-evolution/homo-antecessor/ ↑
22. Source: https://www.smithsonianmag.com/science-nature/homo-antecessor-common-ancestor-of-humans-and-neanderthals-143357767/ ↑
23. At: https://www.yourgenome.org/stories/evolution-of-modern-humans ↑
24. At: https://science.sciencemag.org/cgi/doi/10.1126/science.abh3169 ↑
25. Source: https://www.nationalgeographic.com/science/article/puzzling-skull-discovery-may-point-previously-unknown-human-ancestor ↑
26. At: https://www.bbc.co.uk/news/science-environment-57432104 ↑
27. See: https://www.discovermagazine.com/planet-earth/homo-longi-extinct-human-species-that-may-replace-neanderthals-as-our ↑
28. At: https://www.cell.com/the-innovation/fulltext/S2666-6758(21)00056-4 ↑
29. See: https://www.bbc.co.uk/news/science-environment-57432104 ↑
30. See: https://www.discovermagazine.com/planet-earth/homo-longi-extinct-human-species-that-may-replace-neanderthals-as-our ↑
31. Source: Natural History Museum at https://www.nhm.ac.uk/discover/who-were-the-neanderthals.html ↑
32. At: https://www.britannica.com/topic/Neanderthal ↑
33. Source: LiveScience at https://www.livescience.com/28036-neanderthals-facts-about-our-extinct-human-relatives.html
34. See: Slon, V. et al. Nature https://doi.org/10.1038/s41586-018-0455-x (2018), and https://www.nature.com/articles/d41586-018-06004-0 ↑