Oldest European forefather was Italiano

A pair of ground-breaking papers in Nature last week described the oldest European fossils of modern humans.

As a country they are famous for their pizza, their pasta and currently, their president. Now, Italy can make a claim to fame for hosting the remains of Europe’s oldest modern humans.

Two teeth discovered at Grotta del Cavallo in southern Italy, first assigned to Neanderthals, can now be classified as modern human. What’s more, the two deciduous molars have been redated to 45-43,000 years old – the oldest fossil evidence of our species Homo sapiens in Europe. At this point in time modern humans were on the cusp of entering Europe and displacing their conical-ribbed cousins, the Neanderthals.

A tooth to pick. The Grotta del Cavallo teeth have recalibrated the age for modern humans in Europe. Source: Benazzi, S., et al. 2011 – Nature paper below.

Previously, the oldest fossil evidence of modern humans in Europe came from a site in Romania called Pestera cu Oase or “The Cave with Bones”. The controversial Romanian remains are between 35,000 – 40,500 years old.

Benazzi, S., et al. 2011. Early dispersal of modern humans in Europe and implications for Neanderthal behaviour. Nature doi:10.1038/nature10617.

Redated tooth and jaw: UK’s oldest modern human gets older

In the second revelatory paper published in Nature, a fragment of human upper jaw has been redated to the oldest in northwestern Europe.

The fragment of maxilla was excavated at Kent’s cavern, Devon in 1927 and originally dated to 34,700 – 36,400 years before present (BP). 

However, new analysis and dating of the bone places the fragment between 44,200 – 41,500 years old in age. This would mean that the Devonian dental piece belonged to an individual who lived alongside the last Neanderthals in Europe. 

A) Original dentition of the Kent’s Cavern maxilla outlined in blue; C) Virtually reconstructed Kent’s Cavern maxilla; Internal pulp chambers from left to right of: a Neanderthal, Kent’s Cavern and a modern human upper premolar (B) and canine (D). Source: Higham, T., et al. 2011. Nature.

Previously, the oldest physical evidence of modern humans in Europe as a whole was 41-39,000 years old in age. Modern humans it seems dispersed across the continent a lot earlier than initially thought.

In a close examination of the tooth, 13 dental characteristics are akin to modern humans whereas 4 are more similar to Neanderthals. Thus the tooth undoubtedly belonged to a modern human and not a Neanderthal.

The study also involved Chris Stringer, Head of Human Origins at the Natural History Museum, London. “We’ve gone to microscopic details to show this really is a modern human. You would never find a Neanderthal fossil that had this many modern human features.” he told the BBC.

So the evidence seems conclusive. No bizarre suggestions of a modern human-Neanderthal hybrid like the 24,000 year-old child skeleton found at Lagar Velho, Portugal.

Paper: Higham, T., et al. 2011. The earliest evidence for anatomically modern humans in northwestern Europe. Nature doi:10.1038/nature10484.

A fountain of questions offered by our latest ancestor

Despite the assertions made and many matters resolved by the new research on Australopithecus sediba, questions remain unanswered. How, for example, does Sediba compare to other extinct human species such as “handy man” Homo habilis? Sediba’s brain volume is well short of handy man’s 600cc, who also appears at earlier dates of 2.3 million years ago. Following the news that stone tools predate the genus Homo, what characteristics actually define our genus? Where to draw the line between Australopithecus and Homo? How can Sediba give rise directly to H. erectus when the latter’s brain capacity averages of 850cc? Where do the contemporary Dmanisi fossils fit into this updated story of human evolution?

In the beginning: The mind and heart of where it all began

The human family tree is branching rapidly. Since 2000 alone, at least four new extinct human species have been discovered. Putative others awaiting certification with Latin binomials look set to add further blossom. The tree it seems is becoming more of a bush, worthy of the savannah landscape and scene of our emergence. So, what is it that makes our own species Homo sapiens distinct? How do we differ from the likes of the Neanderthals? Where and when did the classic “modern human” looks appear and our core cultures originate?

The human family tree including all of its current known members. Annotated on are two recent additions - Australopithecus sediba and the genetically-described Denisovan lineage known from a tooth and finger bone discovered in Siberia.

Human origins are notoriously “incomplete and patchy” says Chris Stringer, Professor of Palaeoanthropology at the Natural History Museum, London. The ‘human phase’ in evolution is marked by defining trends in traits. These include an increase in brain size, dietary range and the complexity of our technology; all the way through stone, bronze and iron tools to computers and nanoscale inventions.

Stringer is a major proponent of the Out of Africa 2 theory – the model used to describe our human ancestors dispersal from the African heartland some 80,000 years ago, from which all our roots can be traced. The accepted model dictates that Homo sapiens completely replaced the likes of Homo erectus and the Neanderthals throughout Eurasia during a single mass exodus.

In physical appearances, modern humans differ noticeably in portrait compared to extinct species like Homo heidelbergensis and Homo neanderthalensis (Neanderthals, pictured below). Our faces are tucked under our braincase unlike the primitive, protrusive state of archaic species. We are overall leaner and less robust than our conical-ribbed cousins the Neanderthals even if our brain sizes were on a par, if not inferior.

A selection of Neanderthal skullcaps - note the bulging brow ridges, facial prognathism and low cranial vault unlike the high, domed skull of H. sapiens.

Our behaviour also distinguishes us from the growing crowd of extinct relatives. We live in civilised dwellings and possess the exquisite abilities to paint a picture or intricately thread a needle in order to sew. Language and writing have propelled our species successfully through the cultural revolutions, enabling us to better communicate and record.

All these favourable characteristics must have benefited early Homo sapiens, helping us to conquer the Earth. Interestingly though, due to the many sub-populations in Africa, not all aspects of modern human anatomy and culture were instantaneously knotted. Instead, the assembly of all the modern traits into our H. sapiens ancestors is seen as a kind of genetic fission, dubbed “piecemeal coalescence”. To add to the complications, the African climate was somewhat variable in the early years of our young species which limited population sizes to a few hundred at most. Mitochondrial Eve and her companions it seems were in no way destined for world dominance.

The sites bearing human fossils with the earliest recognisable modern features are exotically named places such as Omo Kibish and Herto, from Ethiopia in East Africa. In age the fossils are 195-160 thousand years old which is in accordance with the predicted genetic age for the origins of H. sapiens. Even older is a skull from Florisbad, South Africa that dates to 260 thousand years ago. The Florisbad skull possesses an array of features intermediate between H. sapiens and our supposed direct Africa ancestor – H. heidelbergensis. If one thing then is clear, it’s that the appearance of our species in the fossil record was not.

Human remains from Israel dating to ca 125,000 years ago further distort the already fuzzy picture of early H. sapiens. These younger fossils constitute the earliest defining evidence of our species roaming outside of Africa. The enigmatic skullcaps aren’t typically modern human though and instead exhibit some classic Neanderthal features such as strong brow ridges. The common consensus now is that the Israel fossils represent an early wave of H. sapiens from Africa, pre-dating the archetypal migration categorised as Out of Africa 2 (OOA2).

In light of shocking new evidence, Out of Africa 2 has been forced to revise. It transpires that DNA from the Neanderthals and the even more mysterious Denisovan group is found in the genetic code of us – modern humans. Only interbreeding can explain such an occurrence. New adaptations of OOA2 are being labelled “leaky replacement” to account for the admixture caused by our ancestors’ apparent promiscuity.

The enigmatic cranium of 'The Hobbit' found on the island of Flores, Indonesia - showing signs of asymmetry?

There is no doubt then that the unauthorised biography of our species cannot yet be written confidently. With constant developments always changing the picture and the branches of our family tree beginning to intertwine, many surprises still lay in wait. Unsolved cases remain, for example the nature of the curious, diminutive hobbits of Flores (left); were they diseased H. sapiens, pygmy individuals or a distinct species altogether? Only time will tell.

Our attempts to classify all that we observe are futile. Debate over the implications of new discoveries and slight contentions will forever ensue, as sure as the eminence of man from within the great apes. If one thing can be agreed upon it’s that human evolution is truly captivating.

-

This article is based on a seminar delivered to the University of Sheffield’s Archaeology Department on (23/03/2011) by Prof. Chris Stringer . The seminar was entitled “Physical and Behavioural Origins of Modern Humans“.

Meet the Denisovans

(From February, 2011)

Scientists have discovered that the exceptionally preserved finger bone found in Denisova Cave in the Altai Mountains of southern Siberia belongs to a distinct group of ancient human-like individuals that roamed the Asian continent alongside modern humans and the Neanderthals.

To add to this, the Denisovans – the group’s assigned name – probably interbred with an ‘Out of Africa’ migrating population of our own species and are responsible for an estimated 4-6% of the genome (entire DNA) of modern day Melanesians.

The revelations, published in articles in Nature, have transformed common knowledge of the relationships of our own species Homo sapiens and have yet again updated the continually growing tree of human evolution.

Dr Ian Tattersall, curator at the American Museum of Natural History, New York said, “the evidence is accumulating that the human evolutionary tree is quite luxuriantly branching. There were multiple species that competed in the evolutionary arena.”

Only 7 months after it was confirmed that Neanderthal DNA survives in present day Europeans, this outstanding new research has come to light to provide more evidence of our human ancestor’s involvement in interbreeding.

The finger bone, initially discovered in 2008 alongside body ornaments such as a bracelet and modern tools including microblades, was used to extract DNA for analytical tests by Professor Svente Pääbo’s team at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.

Results show that the individual to whom the bone pertains was female and possessed DNA and an evolutionary history significantly distinct from ourselves and the Neanderthals. The Denisovan group to which the female – dubbed ‘X-woman’ – belongs shared a common ancestor with the Neanderthals and modern humans H. sapiens around 1 million years ago (MYA). The Denisovan DNA diverged first from the H. sapiens lineage about 800 thousand years ago (KYA) and again 640 KYA from their Neanderthal sister group to create the family tree shown below.

Comparing the DNA from modern humans of diverse ethnicities with samples from Neanderthals and Denisovans reveals the connection between modern day Melanesians and X-woman’s group that is interpreted as a classic signature of interbreeding.

Professor Chris Stringer from the Natural History Museum in London hailed the discovery as “nothing short of sensational” and described the Denisovans as a “new lineage of humans in Asia which we can relate to a particular group of people alive today.”

A tooth uncovered in the same cave back in 2000 was found to contain DNA remarkably similar to that from the finger bone indicating that it derives from a shared Denisovan population which inhabited Asia to an unknown range.

Dr David Reich from Harvard Medical School suggested that “these populations must have been spread across thousands and thousands of miles.”

The tooth also possesses distinguishable features outside the variation and unlike anything seen in either our own species or the Neanderthals, prompting claims of a new species.

However, the authors chose against speculating on the exciting subject of whether the Denisovans constitute a new archaic human species, although Johannes Krause a member of Pääbo’s team did comment that “the evidence is already very strong that we are looking at a previously unknown hominin, and possibly a new species.”

-

The research and information presented in this article can be found in:

Reich, D et al. 2010. Genetic history of an archaic hominin group from Denisova Cave in Siberia. Nature 468, pp 1053-1060.

This article was published by Science Brainwaves and can be found at: http://www.sciencebrainwaves.com/news/post/New-ancestor-to-modern-humans-found-in-Siberia.aspx

How Neanderthal are you?

(From May, 2010)

We know that we shared Europe with them between 30 and 40 thousand years ago (Ka). We know they buried their dead and may have had primitive speech. We even know some of them had red hair alike us. Now, scientific research has provided us with evidence that ancestral lineages of modern humans may also have been getting jiggy with the Neanderthals.

Scientists at the Max Planck Institute for Evolutionary Anthropology have announced a completed draft version of the Neanderthal – Homo neanderthalensis - genome with intriguing results and implications. It appears our mysterious relationship with the Neanderthals is set for further speculation.

The team led by Svente Pääbo, head of the Neanderthal genome project, have sequenced four billion base pairs – roughly 1∙3 fold coverage of the genome or entire genetic code. The genome was compiled from amplified DNA, extracted from 21 Neanderthal bones taken from four European sites in Croatia, Germany, Russia and Spain.

Once mapped, the Neanderthal genome was then compared to five modern human genomes from individuals of French, Han Chinese, Papua New Guinean, Yoruban (west African) and San (southern African) origin for maximum variation.

Now for the revelation! Analytical tests show that the Neanderthal genome is significantly more similar to the genomes of non-African modern humans than Africans. The most plausible explanation for this is interbreeding between Neanderthals and non-African modern human ancestors, estimated to have occurred between 50 and 80 thousand years ago when populations of the two species overlapped in the Levant, Arabia and the Middle-East. One to four per cent of the Eurasian genome could be derived from Neanderthal sequences.

Pääbo commented that ‘Neanderthals fall into our variation and for some parts of the genome I might be closer to Neanderthals than you.’ Chris Stringer, Palaeoanthropologist from the Natural History Museum, London, reasoned that this could have been ‘small scale interbreeding’ with the signs ‘magnified in modern human populations after they increased in size’

In a currently accepted model called Out of Africa Two, modern humans – Homo sapiens - evolved in Africa in the last 200 thousand years and migrated from the continent some 60 to 80 Ka, replacing remaining archaic populations. Neanderthals are known in the fossil record from around 400 Ka when characteristic features such as their protruding nasal region and brow ridge, receding forehead, bell shaped rib cage and low cranial vault appear, to as recently as 26 Ka from a site in Gibraltar. Out of Africa Two doesn’t predict gene flow between the two species but interbreeding dates following migration are compliant.

The scientists were also able to look for areas of the genome that are unique to modern humans and have been altered since our divergence with our so called ‘cousins’ the Neanderthals. It appears genes related to cognitive abilities, metabolism, cranial and upper body skeletal structure have been under positive selection in Homo sapiens since our split from the Neanderthals sometime within the last 500 thousand years.

Sarah Tishkoff, Geneticist, University of Pennsylvania claimed there was ‘no smoking gun – a gene or variant that distinguishes Neanderthals from modern humans, but I think there will be in the future’.

The research has certainly questioned the total replacement model of Out of Africa Two and has placed emphasis on the fossil record to provide us with palaeontological evidence of interbreeding. Contentious fossils showing a mosaic of Neanderthal and modern human characters are known but Stringer added that we should remain ‘cautious’ because they are ‘based on features that occur in low frequency today in modern humans’.

The material for this article can be accessed at:

Green, R.E et al. 2010. A draft sequence of the Neanderthal genome. Science, 328(5979), pp.710-722.

This article was published by Science Brainwaves and can be found at: http://www.sciencebrainwaves.com/news/post/How-Neanderthal-are-you.aspx

Planet of the Apemen: Battle for Earth #1

Blurb: An imaginitive reconstruction and factfile of the interactions between our own species Homo sapiens and another (now extinct) human species Homo erectus. Featuring excerpts courtesy of Chris Stringer, Professor of Palaeoanthropology and Head of Human Origins at the Natural History Museum, London.

The focus is firmly on what advantages we, H. sapiens, possessed that supposedly helped us out-compete H. erectus across Asia around 75 thousand years ago and onwards. H. erectus was a proficient runner and hunter that had inhabited large stretches of Asia for nearly 2 million years. It transpires that language, advanced tools, social networking plus the ability to anticipate enabled modern man to out-think H. erectus. The monotonous Thar desert and the collosal eruption of supervolcano Mount Toba added to the challenges our ancestors faced when migrating through Asia.

There are inaccuracies for example when the narrator states that H. erectus evolves into Homo floresiensis AKA “The Hobbit” in Indonesia – this is one of the most hotly debated topics in the field of human evolution today and a story for another day! What’s more, a recently published study in PLoS One suggests that the two species H. erectus and us, H. sapiens may never have co-existed in Asia after all! Read more here.

Contains a few mildly unnerving scenes involving stone head-bashings and spear stabbings. Also includes some comical make-up on the Homo erectus actors to beef up their brow ridges and “large faces”. Episode 1 sees a cameo role from Angela Wynter (Yolande off Eastenders).

Verdict: Informative and entertaining, 8/10

Link: http://www.bbc.co.uk/iplayer/episode/b0124y9x/Planet_of_the_Apemen_Battle_for_Earth_Homo_Erectus/