̽��ֱ�� of Cambridge - skeleton

Earliest humans had diverse range of body types, just as we do today

jeh98 — Fri, 27 Mar 2015 09:14:54 +0000

One of the dominant theories of our evolution is that our genus, Homo, evolved from small-bodied early humans to become the taller, heavier and longer legged Homo erectus that was able to migrate beyond Africa and colonise Eurasia. While we know that small-bodied Homo erectus – averaging less than five foot and under eight stone – were living in Georgia in southern Europe by 1.77 million years ago, the timing and geographic origin of the larger body size that we associate with modern humans has, until now, remained unresolved.

But a joint study by researchers at the Universities of Cambridge and Tübingen (Germany), published today in the Journal of Human Evolution, has now shown that the main increase in body size occurred tens of thousands of years after Homo erectus left Africa, and primarily in the Koobi Fora region of Kenya. According to Manuel Will, a co-author of the study from the Department of Early Prehistory and Quaternary Ecology at Tübingen, “the evolution of larger bodies and longer legs can thus no longer be assumed to be the main driving factor behind the earliest excursions of our genus to Eurasia”.

Researchers say the results from a new research method, using tiny fragments of fossil to estimate our earliest ancestors’ height and body mass, also point to the huge diversity in body size we see in humans today emerging much earlier than previously thought.

“What we’re seeing is perhaps the beginning of a unique characteristic of our own species – the origins of diversity,” said Dr Jay Stock, co-author of the study from the ̽��ֱ�� of Cambridge’s Department of Archaeology and Anthropology. “It’s possible to interpret our findings as showing that there were either multiple species of early human, such as Homo habilis, Homo ergaster and Homo rudolfensis, or one highly diverse species. This fits well with recent cranial evidence for tremendous diversity among early members of the genus Homo.”

“If someone asked you ‘are modern humans 6 foot tall and 70kg?’ you’d say ‘well some are, but many people aren’t,’ and what we’re starting to show is that this diversification happened really early in human evolution,” said Stock.

̽��ֱ��study is the first in 20 years to compare the body size of the humans who shared the earth with mammoths and sabre-toothed cats between 2.5 and 1.5 million years ago. It is also the first time that many fragmentary fossils – some as small as toes and tiny ankle bones no more than 5cm long – have been used to make body size estimates.

Comparing measurements of fossils from sites in Kenya, Tanzania, South Africa, and Georgia, the researchers found that there was significant regional variation in the size of early humans during the Pleistocene. Some groups, such as those who lived in South African caves, averaged 4.8 feet tall; some of those found in Kenya’s Koobi Fora region would have stood at almost 6 foot, comparable to the average of today´s male population in Britain.

“Basically every textbook on human evolution gives the perspective that one lineage of humans evolved larger bodies before spreading beyond Africa. But the evidence for this story about our origins and the dispersal out of Africa just no longer really fits,” said Stock. “ ̽��ֱ��first clues came from the site of Dmanisi in Georgia where fossils of really small-bodied people date to 1.77 million years ago. This has been known for several years, but we now know that consistently larger body size evolved in Eastern Africa after 1.7 million years ago, in the Koobi Fora region of Kenya.”

“We tend to simplify our interpretations because the fossil record is patchy and we have to explain it in some way. But revealing the diversity that exists is just as important as those broad, sweeping explanations.”

Previous studies have been based on small samples of only 10-15 fossils because techniques for calculating the height and body mass of individuals required specific pieces of bone such as the hip joint or most of a leg bone. Stock and Will have used a sample size three times larger, estimating body size for over 40 specimens contained in collections all over Africa and Georgia, making it the largest comparative study conducted so far.

Instead of waiting for new fossils to be discovered and hoping that they contained these specific bones, Stock and Will decided to try a different approach and make use of previously over-looked fossils.

In what Stock describes as a “very challenging project,” they spent a year developing new equations that allowed them to calculate the height and body mass of individuals using much smaller bones, some as small as toes. By comparing these bones to measurements taken from over 800 modern hunter-gatherer skeletons from around the world and applying various regression equations, the researchers were able to estimate body size for many new fossils that have never been studied in this way before.

“In human evolution we see body size as one of the most important characteristics, and from examining these ‘scrappier’ fossils we can get a much better sense of when and where human body size diversity arose. Before 1.7 million years ago our ancestors were seldom over 5 foot tall or particularly heavy in body mass.

“When this significant size shift to much heavier, taller individuals happened, it occurred primarily in one particular place – in a region called Koobi Fora in northern Kenya around 1.7 million years ago. That means we can now start thinking about what regional conditions drove the emergence of this diversity, rather than seeing body size as a fixed and fundamental characteristic of a species,” said Stock.

Inset images – the landscape of the West Turkana region of Kenya where the 'Nariokotome boy' skeleton was discovered, credit Manuel Will; table of estimated heights and weights of early Homo during the Pleistocene.

New research harnessing fragmentary fossils suggests our genus has come in different shapes and sizes since its origins over two million years ago, and adds weight to the idea that humans began to colonise Eurasia while still small and lightweight.

What we’re seeing is perhaps the beginning of a unique characteristic of our own species – the origins of diversity.

Jay Stock

Cast of the 'Nariokotome boy' (Homo ergaster) skeleton

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Functioning ‘mechanical gears’ seen in nature for the first time

fpjl2 — Thu, 12 Sep 2013 18:05:28 +0000

̽��ֱ��juvenile Issus - a plant-hopping insect found in gardens across Europe - has hind-leg joints with curved cog-like strips of opposing ‘teeth’ that intermesh, rotating like mechanical gears to synchronise the animal’s legs when it launches into a jump.

̽��ֱ��finding demonstrates that gear mechanisms previously thought to be solely man-made have an evolutionary precedent. Scientists say this is the “first observation of mechanical gearing in a biological structure”.

Through a combination of anatomical analysis and high-speed video capture of normal Issus movements, scientists from the ̽��ֱ�� of Cambridge have been able to reveal these functioning natural gears for the first time. ̽��ֱ��findings are reported in the latest issue of the journal Science.

̽��ֱ��gears in the Issus hind-leg bear remarkable engineering resemblance to those found on every bicycle and inside every car gear-box. Each gear tooth has a rounded corner at the point it connects to the gear strip; a feature identical to man-made gears such as bike gears – essentially a shock-absorbing mechanism to stop teeth from shearing off.

̽��ֱ��gear teeth on the opposing hind-legs lock together like those in a car gear-box, ensuring almost complete synchronicity in leg movement - the legs always move within 30 ‘microseconds’ of each other, with one microsecond equal to a millionth of a second.

This is critical for the powerful jumps that are this insect’s primary mode of transport, as even miniscule discrepancies in synchronisation between the velocities of its legs at the point of propulsion would result in “yaw rotation” - causing the Issus to spin hopelessly out of control.

“This precise synchronisation would be impossible to achieve through a nervous system, as neural impulses would take far too long for the extraordinarily tight coordination required,” said lead author Professor Malcolm Burrows, from Cambridge’s Department of Zoology.

“By developing mechanical gears, the Issus can just send nerve signals to its muscles to produce roughly the same amount of force - then if one leg starts to propel the jump the gears will interlock, creating absolute synchrony.

“In Issus, the skeleton is used to solve a complex problem that the brain and nervous system can’t,” said Burrows. “This emphasises the importance of considering the properties of the skeleton in how movement is produced.”

"We usually think of gears as something that we see in human designed machinery, but we've found that that is only because we didn't look hard enough,” added co-author Gregory Sutton, now at the ̽��ֱ�� of Bristol.

“These gears are not designed; they are evolved - representing high speed and precision machinery evolved for synchronisation in the animal world.”

Interestingly, the mechanistic gears are only found in the insect’s juvenile – or ‘nymph’ – stages, and are lost in the final transition to adulthood. These transitions, called ‘molts’, are when animals cast off rigid skin at key points in their development in order to grow.

It’s not yet known why the Issus loses its hind-leg gears on reaching adulthood. ̽��ֱ��scientists point out that a problem with any gear system is that if one tooth on the gear breaks, the effectiveness of the whole mechanism is damaged. While gear-teeth breakage in nymphs could be repaired in the next molt, any damage in adulthood remains permanent.

It may also be down to the larger size of adults and consequently their ‘trochantera’ – the insect equivalent of the femur or thigh bones. ̽��ֱ��bigger adult trochantera might allow them to create enough friction to power the enormous leaps from leaf to leaf without the need for intermeshing gear teeth to drive it, say the scientists.

Each gear strip in the juvenile Issus was around 400 micrometres long and had between 10 to 12 teeth, with both sides of the gear in each leg containing the same number – giving a gearing ratio of 1:1.

Unlike man-made gears, each gear tooth is asymmetrical and curved towards the point where the cogs interlock – as man-made gears need a symmetric shape to work in both rotational directions, whereas the Issus gears are only powering one way to launch the animal forward.

While there are examples of apparently ornamental cogs in the animal kingdom - such as on the shell of the cog wheel turtle or the back of the wheel bug - gears with a functional role either remain elusive or have been rendered defunct by evolution.

̽��ֱ��Issus is the first example of a natural cog mechanism with an observable function, say the scientists.

Inset image: an Issus nymph

For more information, please contact fred.lewsey@admin.cam.ac.uk

Previously believed to be only man-made, a natural example of a functioning gear mechanism has been discovered in a common insect - showing that evolution developed interlocking cogs long before we did.

In Issus, the skeleton is used to solve a complex problem that the brain and nervous system can’t

Malcolm Burrows

Mechanical gears in jumping insects

Burrows/Sutton

Cog wheels connecting the hind legs of the plant hopper, Issus

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Pre-closure celebrations at the Museum of Zoology

amb94 — Thu, 16 May 2013 10:52:42 +0000

̽��ֱ��Museum was awarded initial support from the Heritage Lottery Fund (HLF) for the ‘Animals Galore – preserving and safeguarding diversity’ project in January 2013. ̽��ֱ��project aims to completely refurbish the display spaces of the Museum, to create a Learning Space and School Room and to build new Stores with more space, state-of-the-art preservation conditions and guided public access. ̽��ֱ��project aims to display and illuminate the history of animal life. New interpretation will tell some of the stories behind the collections and the people associated with them, such as Charles Darwin, Alfred Russel Wallace, Hugh Edwin Strickland and Hugh Cott. It will also explore the science behind the understanding of animal diversity and the threats to it, and explain how the community of conservation scientists in Cambridge are seeking to preserve biodiversity.

Visit the museum before the transformation begins. Saturday June 1st is the last day the museum will be open to the public until 2016. Visit between 11 and 4 for free hands on activities, behind the scenes tours, story telling and more. Add a butterfly to the swarm of monarch butterflies in the galleries, make your own museum specimen to take home with you, have a go at being a museum curator and hear stories about the amazing Finback Whale skeleton that hangs above the museum.

During the May half term holidays the Museum will be hosting a number of events to celebrate the proposed changes set to happen here. ̽��ֱ��museum will be open on Bank Holiday Monday 27th May from 11-4. On Tuesday 28th and Thursday 30th May from 11-12 and 2-3 interactive gallery talks will take place in the museum: ̽��ֱ��Animal Awards. Hear the nominations and vote for the animals you think are the spookiest, most disgusting, most surprising or with the best adaptation. There will also be activity packs available all week with museum trails and other activities, and chances for you to tell us your museum favourites.

“ ̽��ֱ��Museum of Zoology is wonderful space, full of beautiful specimens from mammal skeletons to mollusc shells. We are excited about the proposed changes to the museum, and the opportunity to refresh the displays to showcase the amazing collections held here. ̽��ֱ��new learning space will give us the capacity to teach groups in the museum and, when not being used for school groups, the space for more interactive displays. These celebrations in May will give people the chance to enjoy the museum before it closes, and to have their say about what they like about and would like to see in the museum.” (Roz Wade, Education and Outreach Officer)

̽��ֱ��museum will have an active outreach programme while it is closed, details of which will be available on the website (www.museum.zoo.cam.ac.uk) and through its facebook page. There are also projects allowing digital access to the collections, including the Animal Bytes blog telling stories behind the collections (www.animalbytescambridge.wordpress.com).

̽��ֱ�� ̽��ֱ�� Museum of Zoology, Cambridge will be closed to the public from June 2nd 2013. Subject to planning permission, the museum will be undergoing a major redevelopment.

These celebrations in May will give people the chance to enjoy the museum before it closes, and to have their say about what they like about and would like to see in the museum

Roz Wade

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