Thursday, 9 July 2020

Out of Africa 1, the Evolution of Man

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Primates evolved 55 million years ago (MYA) ago in a world very different to our own.
Crab-eating_Macaques, Bernard Dupont, 

10 million years before, there had been a massive asteroid strike (or strikes) causing a 'mass extinction event' including most non avian dinosaurs, initiating a golden age for mammals.
The main land masses were closer than today. Eurasia and America were just separating; Australia and Antarctica were much closer and India was still an island south of Eurasia.
It was very hot and steamy, in no small part due to greenhouse gases (later sequestrated into our fossil fuels and lying frozen in Siberian peat bogs) with equatorial forests stretching all the way to Antarctica.
It was an ideal world for the evolution and spread of a teeming population of tree dwellers and small mammals.

But it was also, for several reasons,  a climate maximum, heralding an inexorable cooling over many millions of years leading up to the Last Glacial Maximum about 19,000 BC.
Over this long period, tropical forests eventually shrank to the equatorial regions, being replaced by deciduous forests, grass lands and deserts. Permanent ice eventually formed at the poles. (Non human) Primates eventually retreated from Europe, leaving only the Barbary apes of Gibraltar.
Current Primate range Napier and Napier, Wiki
This change was slow and 25 MYA there was still plenty of space for the Great Apes to evolve and flourish in the equatorial forests through till about 15 MYA when the shrinkage of their habitat really began to impinge on the species.
From our tree-dwelling forebears mankind inherited  forward-looking eyes, acute binocular vision (more often seen in predators) and grasping hands .
While there are many interesting suggestions, there is no fully accepted explanation of why our forbears moved to an erect posture and a bipedal (striding) gait as opposed to what bother apes and monkeys do when they walk in the open.
There is, however, a prelude in how apes use their upper limbs for grasping, manipulating (feeding and grooming) and their rear limbs for walking along branches and apes they tend to sit erect when feeding or resting. The potential for change was certainly there already.
Most Apes and monkeys remained in the shrinking jungles, but some monkeys (e.g. baboons), and some apes (e.g. chimps and Australopithecus) moved into the savanna (mixed grass/woodland) that was spreading out over East and Northern Africa.
To use a very archaic term, the Genus Australopithecus could be described as a ‘missing link’ between Apes and Homo (having features of both). They evolved around 4.2 million years ago, becoming widespread, eventually dying out about 1.9 million years ago.
They were the first of our ancestors to walk erect on two legs, sleeping in the security of trees at night. They had brains roughly 35% of the size of a modern human brain. Most were slender and covered in fur. The larger of the Genus reached 1.4 meters though females were distinctly smaller.

The name comes from a combination of Greek and Latin, meaning ‘Southern Ape’ (from a full specimen discovered in South Africa).
They lived on fruit, vegetables, and tubers, and perhaps easy-to-catch animals such as small lizards.
The ‘Genus’ Australopithecus is defined as a group of ape species and subspecies that had features between apes and ‘homo’. In other words they walked erect.
We have no way to be sure if they are all as closely related as we think, we have lumped them together on similarities often on the basis of fragmentary evidence. Some anthropologists propose splitting off some of them into other existing genera (or using additional suggested genera). see here
This problem of classifying their finds is one of the great challenges for archaeologists and anthropologists who use morphology, habitat and behaviour as a guide to species, subspecies and genera (more on this later).
Cutting ties 
Genus Homo diverted from the Genus Pan around 5 million years ago, as measured by differences in DNA. Genus Pan is our closest relatives amongst the apes, chimpanzees being their only surviving representatives. 
In Genus Homo two chromosome pairs fused to reduce our chromosomes to 23 pairs instead of the 24 pairs in all other apes, decisively separating Homo from all other surviving apes.
We currently need living, dividing, cells to count chromosomes, so we don’t know when this reduction happened but it is most likely early. We also don’t know if Australopithecus had this too, but it is definitely possible.

Genera, Species and Subspecies
The concept of a species seems simple enough: (the largest grouping of organisms that can crossbreed with one another and produce fertile offspring).  A ‘genus’ is a group of related species with a common ancestor, and subspecies are groups within a species that look different, sometimes significantly, so but still readily crossbreed if given the opportunity.
'Polytypic' can refer to a Genus (with lots of species) but more often refers to a species with lots of subspecies. The main species of homo over time were polytypic.
‘Breeds’ of domesticated species (like the multiple types of dogs, horses etc) are a special example of ‘subspecies’. If dogs were extinct and only a few partial remains were available, an archaeologist today would likely think he had discovered several different species, when in fact domesticated dogs, some wild dogs, and various wolves are now all recognised as part of the one species!

Early man cannot compete with the diversity of Canis Lupus Familiaris (domesticated dogs) in terms of their current diversity. The evidence is still fragmentary, especially in the distant past, but over time we have begun to understand that interbreeding of different-looking contemporary forms of Homo was much more common than we ever realised.
It's hard to be absolutely sure, but much of what we assumed were different contemporary species were subspecies. 
Part of this new understanding followed advances in understanding of how evolution actually works, and after we found modern man interbred with Neanderthals and Denisovans when reaching Eurasia from Africa (more on this later).

Evolution and subspecies.
Evolution occurs when there is variation between individuals within a species and some of these variations have an advantage for survival and reproduction, either dependent on a certain habitat or an over all advantage.
Sub-species occur in nature when groups of the same species become separated over place or time and/or they adapt to local environments or simply experience genetic drift. 

With several subspecies of early man (capable of interbreeding). Each had particular mutations that might be an advantage 'over all' or in certain habitats. Interbreeding, ensured that any differences that might prove advantageous could be combined and not lost forever. Specific combinations may work well together and wider variation allows penetration into niche habitats and faster adaptation to habitat change

This interbreeding and evolution within subspecies leads to the concept of 'chronospecies'. A chronospecies is a species which slowly changes over time until it cannot be considered as the same species as the originating genetic line (had they existed at the same point in time). 
Chrono-species Ian Alexander, Wiki

It might be just genetic drift and different environments causing such differences that eventually interbreeding becomes unlikely (e.g. loss of sexual attraction, mating rituals or physical differences).

Natural selection can favour  interbreeding to foster a larger gene pool with diversity, but it can also favour separation of subspecies into separate species ('speciation') .
This happens when the 'in-between' or older varieties become at a such disadvantage relative to the new variety that the benefits of the larger gene pool to overall adaptation (of the species) is outweighed by the cost.
Such a thing occurs more rapidly when the habitat of the subspecies is very different and the adaptation needed for each niche habitat is very different .
In the development of a chronospecies, each change is small and interbreeding occurs along the 'chain'. The point at which we would say a new species has 'arisen' is arbitrary. The evolution of man followed just such a pattern.

There is still considerable uncertainty and debate, but the minimalist view (currently favoured) leaves Homo Habilis, Homo erectus and Homo sapiens (and their respective contemporaries) as the only three species of Homo.  
Encyclopaedia Britannica  see here
Gone are the multiple ‘species’ that were proclaimed every time archaeologists found remains that varied from what had been found before.
We need to be cautious not to see evolution as always a march from primitive to more advanced, though this can happen.
Natural selection doesn't care about human value judgements, it only cares about adaptation (survival) and reproduction. It just so happens that many of the adaptations leading to modern man had a huge survival advantage. 

Homo Habilis
Homo habilis was one of the earliest species of ‘man’ (homo), 2.4 to 1.4 MYA.
The arrival of Habilis marks the official start of Genus Homo.
‘Habilis’ is Latin, the same root as ‘able’ and has a number of related meanings like ‘skilful’. ‘Homo Habilis’ has been translated as ‘handy man’, tool maker.
Sculpture H. Habilis, √Člisabeth Dayn√®s 
We initially used evidence of fashioning of tools as the  defining feature of Genus Homo, but advanced types of Australopithecus have been shown to fashion primitive tools maybe even a million years before.
We don’t know for sure if Homo Habilis is a direct ancestor of modern man as we first believed, and we don't know his relationship with a number of other early forms of homo, whether they were separate species or subspecies  (like H. rudolfensis, another contender for the title of being our ancestor).
The oldest homo remains, LD 350-1, (as yet unclassified into a species) is from Ethiopia 2.8–2.75 million years ago (mya) confirming that 'homo' evolved in Africa (in the savanna).

Homo spread to Asia about 2 million years ago. There were manufactured tools from 2.1 MYA found in Shangchen, China and in the nation of Georgia 1.85–1.77 MYA. This was thought to be  Homo erectus but the Georgian specimens and brain size are decidedly primitive, so it might have been a variety of Homo Habilis.

Homo Erectus
The award for the first species of man that spread beyond Africa usually goes to Homo Erectus.
H. Erectus lived from between 2 MYA to as recent as 110,000 years ago, overlapping H. Habilis by almost half a million years and Homo Sapiens by about 200,000 years. Being a Chronospecies the later versions of H.Erectus would be more advanced.
H. Erectus dispersal, Sheila Mishra Here
It is the longest living of all human species, being present nine times as long as our own species, Homo sapiens.

H. Erectus was highly successful, and mobile, spreading over Africa and Eurasia
It was H. Erectus that first began to hunt medium-large animals in groups (such as bovines or elephants), moving to a diet richer in meat. Erectus would have had some tribes that routinely followed migrating herds.

Erectus tamed fire a million years ago , and maybe earlier and he made water craft probably for fishing, but was able to colonise at least a few islands (eg Indonesia) 

With longer legs and relatively shorter arms (no longer climbing trees) and loss of hair, allowing running distances in the heat H. Erectus was bigger, faster and smarter (with an average brain capacity at least a third bigger than H. Habilis).

There is a conflict in the best pelvis for running on two feet and the ability to deliver babies with large heads.
In 'Modern man ' children are dependant on their parents for longer (with more monogamous bonding in parents) allowing considerable brain growth after birth. Larger brains require a lot of energy and are best supported in hunter-gatherers by cooking and using more meat in the diet, requiring co-operative hunting of large animals.

H. Erectus is a chronospecies with a very long history and a very wide range. He evolved over time and there were many subspecies. The larger subspecies had body proportions similar to modern man, with distinctly larger brains (up to 60% of H. Sapiens). This is in sharp contrast to the smaller and earlier subspecies (or species).

The main African versions is often called ‘H. ergaster’. Homo heidelbergensis (700,000 to 300,000 years ago in Africa and Europe) is the subspecies (or maybe chronospecies) closest to H. Sapiens.

The oldest H. Erectus remains are found in Kenya. The majority view is that H. Erectus also evolved in Africa and spread over Euro-Asia via the Middle East to Asia (including China and Indonesia) about 2 MYA. As said, he also made it to islands and must have made primitive water craft. There is some debate when H. Erectus arrived in Europe, whether it was soon after or somewhat delayed because ‘he’ preferred a warmer climate.

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Tuesday, 19 May 2020

The Missing Neolithic Farmers of Old Europe

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 In last month’s blog we discussed the dawn of the Neolithic Age. It is believed that the transition to  
Urfa Man Turkey 9,000 B.C.
Neolithic farming occurred in the Levant, most likely when a 1200 year drought brought a catastrophic end to the local Mesolithic Age. A few permanent settlements survived this catastrophe (like Tell Qaramel near modern day Aleppo) but the shortage of forage likely forced greater reliance on cultivation of 'wild' strains of plants and grains (and presumably primitive irrigation).
 At first ‘pre pottery Neolithic’ settlements (PPNA, 10,000–8,800 BC) were similar to the Natufian Mesolithic villages except for being larger and (much) more sophisticated (e.g. Jericho).
There were variations over time and distance but in the later ‘a-ceramic’ period (PPNB, 8,800–6,500 BC) Anatolia (Turkey) emerged as a Neolithic powerhouse, incorporating animal husbandry, 'domesticated' strains of grain and other crops and farming techniques some of which were discovered elsewhere (such as Mesopotamia and the Zagros region of western Iran).
It was Anatolian farmers and fisher folk that island hopped to reach Greece (around 7000 BC, before the official start of the pottery Neolithic Age in the Middle East, 6,400 BC). They established a large number of thriving maritime settlements  over the northern Mediterranean and eventually the Atlantic coast. They followed two land routes into Europe, eventually reaching Scandinavia and crossing the English Channel around 4,000 BC ( the map to the right and below is only to roughly show some of these routes).
This was not the spread of ideas, this was large scale movement of farmers, their crops and animals. They intermarried with the nomadic and Mesolithic hunter-gatherers of Europe but they dominated them with their superior numbers.They cleared virgin forests, tilled the soil and domesticated local plants and animals. 
It was perhaps in central and south eastern Europe that saw their greatest achievements supported by a vast trade network. There they lived in heavily fortified settlements, like Sesklo in Greece which in 5000 BC may have housed  an incredible 5,000 people, one and half millennia before the invention of the wheel and only a few hundred years after the first (Sumerian) city (Eridu in Mesopotamia) was said to be established.
Archaeologists have found the oldest gold treasure in the world in Bulgaria (4,600 BC to 4,200 BC)  
Varna necropolis, Bulgaria Wiki
the earliest evidence of copper smelting in Serbia (5500-5000 BC, 1.5-2 millennia before the Copper Age) and the world's oldest salt mine in Hallstatt Austria (about 5,000 BC).
The 'Old European culture' varied over time and distance but their numbers and sophistication continued to grow with the arrival of the potter’s wheel and ox-drawn carts. A few archaeologists have even suggested some of their pottery symbols were a form of proto-writing hundreds of years before the Sumerian pictograms.
It was they that built many of the first European megaliths, long barrows and passage tombs. Some of the ‘mega settlements’ in central and South Western Europe around Western Ukraine (4000–3500 BC) may have housed 20,000 to 46,000 people.
Almendres Cromlech from 6,000 BC Portugal, Wiki
The first Neolithic farmers of old Europe reached their peak around 4,000 BC.
Around 3,500 BC their population began to collapse relatively abruptly. In many regions the depopulation was catastrophic. Britain  lost 90 % of its Neolithic population in three hundred years. In a few areas it was almost 100%, in other areas it was less and a few areas were relatively spared.

The Pelasgians, Minoans and Leleges (Greece), the Iberians and Basques, the Nuragic people of Sardinia, the Sicans and the Elymians of Sicily and the Etruscans are all suggested (with different levels of certainty) to be related to these older Europeans. See my earlier discussion of the first people of Greece here.
The artwork of these ‘old Europeans’ lead the celebrated archaeologist Marija Gimbutas to suggest they were ‘matristic’ and peaceful, worshiping the mother goddess and that they were overwhelmed by the war-like ‘paternal’ (fairer) Indo-Europeans pastoralists from the great Steppe, with their horses, weapons and male Gods.
Hamangia culture Bulgaria, wiki
There is no positive evidence for such a whole sale conflict and besides, the Indo-Europeans didn’t begin arriving in any numbers till 500 years after the start of the catastrophe, moving in to fill a relative vacuum.The Indo-Europeans weren't to finish their settlement of Europe till about 1,000 BC (towards the end of the European Bronze Age).
What happened to the missing Neolithic Farmers of old Europe?
History is replete with examples of sudden inexplicable collapse and disappearance of Neolithic cultures and civilisations, leaving only sadness and mystery behind. The usual ‘suspects’ warfare, climate change and soil exhaustion are not satisfactory here.
The old Europeans were sophisticated farmers who knew all about organic fertiliser and pasture rotation. The depopulation seemed to have hit different areas at slightly different times but a population ‘bust’ seemed much more likely after exponential population growth, as if it was punishing success.
Perhaps the population growth made food security more precarious and unable to respond to an external shocks. In some cases there was an increase in population nearby suggesting people were fleeing from something.
It is now suspected that the population density and unhygienic conditions led to an outbreak of disease, which spread from village to village over the trading routes. 
We already know just how devastating an epidemic can be in a population that has no natural immunity and the shift to Neolithic lifestyle made people much more vulnerable to epidemics.
There was already a long tradition 6500 BC -2000 BC in central and south-eastern Europe of villagers burning their whole village and moving every eighty years or so. Sometimes they would return to an old site much later and rebuild on the rubble. Was it denying another tribe use of the village while allowing the land to lay fallow? Was there religious or social reasons? We don’t really know, but it could have been related to vermin or disease.
If it was to cope with disease, burning their homes and fleeing to other areas no longer worked for the Neolithic farmers.
The scale of devastation with some areas massively depopulated (some less affected and a few relatively spared) is reminiscent of a later catastrophe, the Black Death and it seems that they were dealing with something of similar virulence. In a previous article we discussed the evidence emerging that they were indeed dealing with first pandemic of the Plague, with an early primitive strain but at least equally as devastating.here
Where did the plague initially come from?  We know its ancestor Yersinia pseudotuberculosis came from the far east so this early form of Plague likely came via the Great Eurasian Steppe.
It is pure speculation but possibly a more peaceful contact with Indo-European traders still proved fatal to the old people of Europe, long before the Indo-Europeans moved into Europe in any numbers.

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