Sunday, August 01, 2021

On the origin of humans and evolution

Humans, chimpanzees and bonobos were descended from a single ancestor species that lived 6 to 7m years ago. Humans and their closest cousins share 98.8% of their DNA, according to the American Museum of Natural History. The same DNA can behave differently — we share about 96% of our DNA with gorillas.

Charles Darwin (1809-1882) in his 1871 book 'The Descent of Man,' speculated that it was “probable” that humans originated in Africa because our two closest living relatives — chimpanzees and gorillas — live there. However, he also acknowledged that a large extinct ape once lived in Europe millions of years ago, leaving time for our earliest ancestors to move to Africa. Darwin concluded, “it’s useless to speculate on the subject.”

We now know the location of the cradle of humanity and at least 21 human groups can be identified from 6 to 7m years ago to modern humans that have developed from about 300,000 years ago.

What we also know is that Homo sapiens (Latin: “wise man”) is the species to which all modern human beings belong and that is among the genus Homo (man or human).

Homo sapiens is the only group that is not extinct.

It took all of human history up to 1804 for the world's population to reach 1bn. But the next billion came only 100 years later, in 1927. And after that, the rate of growth accelerated, 3bn in 1959, 4bn 1974, 5bn 1987, 6bn in 1999, 7bn in 2011, 7.9bn in 2021, and projections by the United Nations of  9.8bn in 2050 and 11.2bn in 2100.

Carolus Linnaeus (1707-1778), the Swedish botanist, zoologist, taxonomist, and physician, first applied the name Homo sapiens in 1758.

Darwin and Wallace

Evolution is the process where organisms change over time in response to different factors in their environment. All organisms, including humans, evolve over time. It occurs through natural selection and this is what has shaped every organism living today.

Darwin and Alfred Russel Wallace (1823-1913) are jointly credited with independently developing the theory of evolution by natural selection. They agreed to present papers in London on it in 1858. However, Darwin has generally overshadowed Wallace since the publication of Darwin's book 'On the Origin of Species' in 1859.

'On the Origin of the Species' explained how new species evolved. Darwin argued that tiny variations between individuals could give one or the other a competitive advantage. He said in generation after generation those tiny advantages were then passed down, or selected until the species eventually changed.

Darwin had been building up evidence for his theory of natural selection for more than 20 years after his return from South America in 1836, while Wallace had been collecting bird and animal samples in the Malay Archipelago (comprising modern Malaysia, Indonesia and Singapore) since 1854.

Darwin defined evolution as "descent with modification" — the idea that species change over time, give rise to new species that share a common ancestor. He did not use the word 'evolution' in his 'On the Origin of the Species' book until the 6th edition in 1872 — "At the present day almost all naturalists admit evolution under some form."

The phrase "Social Darwinism" first appeared in an 1877 article on 'The History of Landholding in Ireland.'

British philosopher Herbert Spencer (1820-1903) coined the phrase "the survival of the fittest" in 1851 and Darwin used it as a synonym for natural selection in the 5th edition of 'On the Origin of the Species' 1869. However, "Social Darwinism" in the decades after Charles Darwin's death was used to justify racism, colonialism, inequality and eugenics that had nothing to do with the process of evolution.

By the way, Darwin never wrote “It is not the strongest of the species that survives, but rather, that which is most adaptable to change.”

Anaximander of Miletus, a Greek philosopher who lived in the 500s BC, is said to have speculated that human ancestors were fish (which was true). However, an examination of the "writings of the Greek philosophers Thales, Anaximander, and Empedocles shows that there is no textual-historical basis to credit the pre-Socratic philosophers with developing a theory of evolution."

A century before Darwin, Frenchman Georges-Louis Leclerc, Comte de Buffon (1707-1788) in his 'Historie Naturelle,' a 44 volume encyclopedia on the natural world, acknowledged the similarities of humans and apes and referred to their common ancestry. Buffon also published 'Les Epoques de la Nature' (1788) where he suggested that the planet was 75,000 years old.

Erasmus Darwin (1731-1802), Charles Darwin's grandfather, who was a medical doctor and also a poet, philosopher, botanist, and naturalist, presented one of the first formal theories on evolution in Zoonomia, or, 'The Laws of Organic Life' (1794-1796).

Google Books Ngram Viewer for 1850-2019

Charles Darwin dropped out of a medical degree course at Edinburgh University in 1827 and his father had him enrolled at Cambridge University to study the classics, botany and theology. The hope was that he would become a pastor of the Church of England.

Having graduated as a Bachelor of Arts in the summer of 1831, John Stevens Henslow, professor of Botany and Mineralogy at Cambridge, got Darwin a place on the HMS Beagle survey ship that left Plymouth, England, in late 1831. The voyage involving mapping the coasts of South America was to take two years but the Beagle would not return to Falmouth, England, until October 1836.

What would eventually be the highlight of Darwin's trip was the arrival in the Galápagos Archilapego, on September 17, 1835. The Beagle anchored in Stephens Bay on Chatham Island, now known as San Cristóbal.

Located about 1,000 km (600 mi) west of continental Ecuador, the archipelago comprises 127 islands, islets and rocks, of which 19 are large and 4 are inhabited.

The Beagle at Ponsonby Sound in the Beagle Channel, Tierra del Fuego, in March 1834; painting by the ship's draughtsman Conrad Martens

Since Darwin's visit, over 60 recorded eruptions have occurred in the islands, from six different shield volcanoes. Of the 21 emergent volcanoes, 13 are considered active.

In a letter to a friend in August 1835, Darwin was excited about the round-the-world trip ahead, and writes, "I look forward to the Galápagos, with more interest than any other part of the voyage."

However he wrote in his diary on arrival, "We landed upon black, dismal looking heaps of broken lava ... Innumerable crabs and hideous iguanas started in every direction as we scrambled from rock to rock."

The ship was in the archipelago for 36 days and Darwin and the crew spent 19 days on land collecting specimens of the wildlife on the main islands. Darwin was particularly interested in the geology of the islands and he also noted the variations of the birds on the different islands.

There was no eureka moment on the Galápagos and the Beagle then set sail for Tahiti.

Five months after returning to England, Darwin met the English ornithologist John Gould (1804-1881) who reviewed the bird specimens brought home by the Beagle crew. Some had labelled the particular islands that they came from. Gould observed that sets of birds were different species rather than “only varieties.” Gould also informed Darwin that 25 of his 26 land birds from the Galápagos were new to science, as well as unique to those islands.

Charles Darwin's pencil sketch on Natural Selection in 1842

Susanah Wedgwood, Charles' mother and a member of the famous Wedgwood pottery family, died when he was 8 years old. Charles married his first cousin, Emma Wedgwood (1808-1896) in January 1839. She was a religious person and she wrote in a letter soon after the wedding "May not the habit in scientific pursuits of believing nothing till it is proved, influence your mind too much in other things which cannot be proved in the same way, & which if true are likely to be above our comprehension."

They had 10 children and 3 of them died young.

Charles Darwin young and old

Charles had long-term medical problems and here an Australian academic speculates that he had a mitochondrial disease that is inherited from the mother and it results in failing to produce enough energy for the body to function properly.

His loving wife Emma helped to calm his anxiety. For example in 1865 the 56-year old Darwin wrote a letter to his physician outlining his travails: "For 25 years extreme spasmodic daily and nightly flatulence; occasional vomiting preceded by shivering, hysterical crying...dying sensations or half faint and copious very pallid urine. Now vomiting and every passage of flatulence preceded by ringing of ears, treading on air and & vision...Nervousness when E leaves me."

On origins of the humans

The Earth is estimated to be 4.54bn years old, plus or minus about 50m years. Scientists have to find the oldest rock on the planet!

James Ussher (1581–1656), Protestant Archbishop of Armagh and Primate of All Ireland between 1625 and 1656, estimated that the age of the Earth dated from "the entrance of the night preceding the 23rd day of October... the year before Christ 4004"; that is, around 6pm on 22 October 4004 BC, per the proleptic Julian calendar.

Ussher was born in Dublin, and in 1650 the world to him was 5,654 years old. The German scientist Johannes Kepler (1571-1630) put the creation date at 3993 BC and Isaac Newton (1642-1727) suggested 3998 BC.

In Northern Ireland, the Protestant Democratic Unionist Party (DUP) still has senior members that believe the Earth now is about 6,000 years old and in 2016 a DUP member of the regional government said: "I long to see the day when every school in Northern Ireland will stand up and teach creationism, and turn away from the peddled lie that is evolution."

In the United States, majorities of the major religions accept evolution but 38% of White Evangelical Protestants in a PEW poll do not.

In a section of the 'On the Origin of the Species' entitled “On the Lapse of Time,” Darwin wrote: "It is hardly possible for me even to recall to the reader, who may not be a practical geologist, the facts leading the mind feebly to comprehend the lapse of time. He who can read Sir Charles Lyell’s grand work on the 'Principles of Geology' … yet does not admit how incomprehensibly vast have been the past periods of time, may at once close this volume."

Among scientists, until the latter half of the 20th century, the consensus was that humans originated either in Europe or Asia. There had been a significant fossil find in Southern Africa but it was not taken seriously.

Neandertal or Neanderthal (tal — a modern form of thal — means “valley” in German) refers to an inhabitant of the Neander Valley of the river Düssel, 13 km (8.1 mi) east of Düsseldorf in the German state of North Rhine-Westphalia.

In August 1856, workers at a limestone quarry discovered likely human bones. There was a partial skull, pelvis and assorted long bones, which later became known as Feldhofer 1, or Neanderthal 1.

William King (1809-1886), a professor of Geology and Mineralogy at Queen’s College in Galway, Ireland, argued that the cranium looked more like that of a chimpanzee than a human, and in 1864 Prof King said it should be placed in a new species, Homo neanderthalensis.

The find was not the first Neanderthal fossil discovery as other Neanderthal fossils had been located earlier but their significance had not been realised — in 1829 at Engis, Belgium, and in 1848 at Forbes Quarry, Gibraltar — were also Neanderthals.

In 1891, Eugène Dubois, a Dutch geographer, discovered remains of what he described as "a species in between humans and apes." Java Man in the then Dutch East Indies was classified as Homo erectus ("human that stands upright"). This was the first hominid remains to be found outside of Africa or Europe.

In 1907 near Heidelberg, Germany, a workman found a fossil in a sandpit just north of the village of Mauer. It was almost complete but for missing premolars and the first two left molars; it was heavily built and lacked a chin and was named Homo heidelbergensis.

This was a significant find as Homo heidelbergensis may have been the common ancestor of Homo sapiens (modern humans) and Homo neanderthalensis

...and then there was a fossil find in Piltdown, East Sussex, England, reported in 1912, but it was declared a hoax in 1953.

In 1924, a fossil discovery in South Africa challenged the view of a Eurasian homeland and revolutionised the study of human evolution.

Raymond Dart (1893-1988), an Australian-born anatomist working at the University of Witwatersrand in Johannesburg, was interested in fossils and in late 1924 he accepted delivery of two boxes of rocks blasted from a limestone quarry near the town of Taung, south of the Great Kalahari Desert, in South Africa.

Dart’s recognition of the humanlike features of the Taung skull, confirmed Darwin's expectation that such ancestral hominin forms would be found in Africa.

Dart found the fossilised mould of a brain with the shape and folds on the brain’s surface which implied it belonged to some kind of human and may have been an ancient human ancestor, Dart thought. He freed the brain’s corresponding face and lower jaw in December 1924.

The fossil was of a child about 3 years old based on its baby teeth and was about 2.8m years old. The Taung Child called Australopithecopus africanus lacked a pronounced muzzle as seen in chimps and gorillas. And the placement of the hole through which the spinal cord exits the bottom of the skull — the foramen magnum — suggested it had an erect posture and walked upright on two legs.

Holes on the Taung Child revealed that an eagle or large predatory bird dropped the creature at the entrance of the cave where the fossil was eventually found.

The fossil data since then show that humans evolved in different places but each of the 21 hominins originated in Africa.

In 2017 an international research team led by Jean-Jacques Hublin of the Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany, and Abdelouahed Ben-Ncer of the National Institute for Archaeology and Heritage, INSAP, Rabat, Morocco, reported that they had uncovered fossil bones of Homo sapiens along with stone tools and animal bones at Jebel Irhoud, Morocco. "The finds were dated to about 300,000 years ago and represent the oldest securely dated fossil evidence of our own species. This date is 100,0000 years earlier than the previous oldest Homo sapiens fossils. The discoveries reported in two papers...reveal a complex evolutionary history of mankind that likely involved the entire African continent."

"We used to think that there was a cradle of mankind 200,000 years ago in east Africa, but our new data reveal that Homo sapiens spread across the entire African continent around 300,0000 years ago. Long before the out-of-Africa dispersal of Homo sapiens, there was dispersal within Africa," said palaeoanthropologist Jean-Jacques Hublin.

Both genetic data of present-day humans and fossil remains point to an African origin of our own species, Homo sapiens. Previously, the oldest securely dated Homo sapiens fossils were known from the site of Omo Kibish in Ethiopia, dated to 195,000 years ago.

According to the US Science magazine "The fossils suggest that faces evolved modern features before the skull and brain took on the globular shape seen in the Herto fossils (see dateline in hart above) and in living people. 'It’s a long story — it wasn’t that one day, suddenly these people were modern," Hublin said. "Neanderthals show the same pattern: Putative Neanderthal ancestors such as 400,000-year-old fossils in Spain have elongated, archaic skulls with specialised Neanderthal traits in their faces."

Homo sapiens' common ancestor with the Neanderthals?

The Smithsonian Institution says that scientists used the molecular clock to estimate how long it took to accumulate the differences between this oldest Neanderthal genome and that of modern humans, and the researchers suggest that a common ancestor lived sometime between 550,000 and 750,000 years ago.

"Comparison of Neanderthal and modern human DNA suggests that the two lineages diverged from a common ancestor, most likely Homo heidelbergensis, sometime between 350,000 and 400,000 years ago – with the European branch leading to H. neanderthalensis and the African branch (sometimes called Homo rhodesiensis) to H. sapiens."

SI says "Our ancestors used stone tools as long as 3.3m years ago and by 1.75m years ago they’d adopted the Acheulean culture, a suite of chunky handaxes and other cutting implements that remained in vogue for nearly 1.5m years. As recently as 400,000 years ago, thrusting spears used during the hunt of large prey in what is now Germany were state of the art. But they could only be used up close, an obvious and sometimes dangerous limitation."

This is a 2016 Nature journal map and since then evidence from Morocco (see above) and South Africa, show that the modern human first evolved in Africa about 300,000 years ago. Scientists said in 2017 that they had sequenced the genomes of 7 people including a boy who lived as a hunter-gatherer 2,000 years ago in South Africa. They were able to estimate that the evolutionary split between Homo sapiens and ancestral human groups occurred 260,000 to 350,000 years ago.

“In this time period, some genetic changes may have happened that make us humans who we are today, and distinct from, for example, Neanderthals,” said population geneticist Mattias Jakobsson of Uppsala University in Sweden, co-leader of the research published in the journal Science.

Neanderthals survived for 400,000 years and then they became extinct 40,000 years ago. They and the Denisovans, another population of early humans who lived in Asia and were distantly related to Neanderthals, shared a common ancestor with us, modern humans.

Prof Chris Stringer of the British Natural History Museum says "Genetic research shows that most people outside of Africa have about 2% Neanderthal DNA. We think that the modern humans who spread into Asia around 60,000 years ago interbred with the Neanderthals. Since these migrants were the ancestors of all people outside of Africa, they took their small bit of Neanderthal DNA with them as they spread out across the world."

Neanderthals evolved in Europe and Asia while modern humans - our species, Homo sapiens — were evolving in Africa.

Prof Stringer adds "Despite their reputation as being primitive 'cavemen,' Neanderthals were actually very intelligent and accomplished humans. These were no 'ape-men'. So it's unfair to them that the word Neanderthal is used as an insult today."

It is not known yet, what may have precipitated the extinction which likely spread over time.

Modern humans developed projectile weapons such as spears and spear-throwers and bows and arrows to enable them to hunt more successfully than Neanderthals.

Of course, there is a lot of speculation and Dutch researchers in 2019 guessed that Neanderthals numbered in mere thousands, within a range of 5,000 to perhaps 70,000 individuals at their peak.

"Did Neanderthals disappear because of us?" asked the researchers, led by bioscience engineer and philosopher Krist Vaesen from the Eindhoven University of Technology in the Netherlands. "No, this study suggests. The species' demise might have been due merely to a stroke of bad, demographic luck."

EU-funded research shows that scientists determined the source of methane that triggered a period of rapid global warming 40,000 years ago. Another study highlighted two cold and dry periods. One began about 44,000 years ago and lasted about 1,000 years. "The other began about 40,800 years ago and lasted six centuries. The timing of those events matches the periods when artefacts from Neanderthals disappear and signs of H. sapiens appear in sites within the Danube River valley and in France, they noted."

The researchers claim that climate shifts would have replaced forest with shrub-filled grassland, and H. sapiens may have been better adapted to that new environment than the Neanderthals were, so they could move in after Neanderthals disappeared.

Competition for scarce resources from humans may also have been a factor as may climate change or imported Homo Sapiens' human diseases.

After all, humans have an example of what large-scale migration can do to indigenous people:


An evolutionary timeline of Homo sapiens "The long evolutionary journey that created modern humans began with a single step—or more accurately — with the ability to walk on two legs. One of our earliest-known ancestors, Sahelanthropus, began the slow transition from ape-like movement some 6m years ago, but Homo sapiens wouldn’t show up for more than 5m years. During that long interim, a menagerie of different human species lived, evolved and died out, intermingling and sometimes interbreeding along the way. As time went on, their bodies changed, as did their brains and their ability to think, as seen in their tools and technologies."

Humans change the word — the good and the bad

Human Family Tree

The 21 human species and the one survivor

Documentary on Evolution and Charles Darwin

A film of Darwin and Wallace on Evolution

Sarawak today is a Malaysian state on the island of Borneo. This photo of Ali (he called himself Ali Wallace and his Malay name is unknown) with European clothes was taken in Singapore in 1862. Wallace wrote of the 15-year old who began working for the Welshman: "When I was at Sarawak in 1855 I engaged a Malay boy named Ali as a personal servant, and also to help me to learn the Malay language by the necessity of constant communication with him. He was attentive and clean, and could cook very well. He soon learnt to shoot birds, to skin them properly, and latterly even to put up the skins very neatly. Of course, he was a good boatman, as are all Malays, and in all the difficulties or dangers of our journeys he was quite undisturbed and ready to do anything required of him."