Archive for the ‘Evolution’ Category

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We walk upright to carry things

March 26, 2012

A new paper reports two studies of Bossou chimpanzees which show that “wild chimpanzees walk bipedally more often and carry more items when transporting valuable, unpredictable resources to less–competitive places”.

Susana Carvalho, Dora Biro, Eugénia Cunha, Kimberley Hockings, William C. McGrew, Brian G. Richmond, Tetsuro Matsuzawa. Chimpanzee carrying behaviour and the origins of human bipedality. Current Biology, 2012; 22 (6): R180 DOI: 10.1016/j.cub.2012.01.052

Summary

Why did our earliest hominin ancestors begin to walk bipedally as their main form of terrestrial travel? The lack of sufficient fossils and differing interpretations of existing ones leave unresolved the debate about what constitutes the earliest evidence of habitual bipedality. Compelling evidence shows that this shift coincided with climatic changes that reduced forested areas, probably forcing the earliest hominins to range in more open settings. While environmental shifts may have prompted the origins of bipedality in the hominin clade, it remains unknown exactly which selective pressures led hominins to modify their postural repertoire to include a larger component of bipedality.  Here, we report new experimental results showing that wild chimpanzees walk bipedally more often and carry more items when transporting valuable, unpredictable resources to less–competitive places.

(more…)

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Of Mice and Vikings

March 24, 2012

A recent paper from a multinational team of researchers from the UK, USA, Iceland, Denmark and Sweden describes studies of mytochondrial DNA (mtDNA)  in mice to track ancient Viking movements.  The mice genetics confirm the movements of the Vikings some 1000 years ago to Britain and Greenland and Iceland. They do not however provide any confirmation of the fleeting Viking presence in Newfoundland.

Viking movements: map from bbc.co.uk

“Modern house mouse populations were sampled across Iceland (9 localities), at Narsaq in Greenland (near the Viking Age ‘Eastern Settlement’) and in the north-west of Newfoundland (near the Norwegian Viking archaeological site at L’Anse aux Meadows, 4 localities).  Ancient DNA was obtained from archaeological house mouse bones. In Greenland, these were from the Norwegian Viking ‘Eastern Settlement’ (3 individuals) and ‘Western Settlement’ (2 individuals), dating from between 1015– 1165 AD. In Iceland, these were from four archaeological sites in the north of Iceland, three of which date to the 10th C (1 individual per site) and one of which dates to the Medieval period or later (1477–1717 AD; 2 individuals”.

E P Jones, K Skirnisson, T H McGovern, M TP Gilbert, E Willerslev, J B Searle. Fellow travellers: a concordance of colonization patterns between mice and men in the North Atlantic region. BMC Evolutionary Biology, 2012; 12 (1): 35 DOI: 10.1186/1471-2148-12-35

(more…)

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6,000 generations since Out of Africa

February 13, 2012

Lately, I have been delving into the fascinating – but somewhat arcane – fields of paleo-anthropology and genetics and biology and archeology. I find I am constantly trying to create a narrative which hangs together and looking for the little details which can enable me to personalise and identify with the narrative. It is a search for little “hooks” onto which I can hang my “hats” of understanding. And one such “hook” which both anchors and enables my imagination is that when looked at in the perspective of individuals in a particular line of descent, the ancient past is not as intangible and unreachable as it might seem.

from Wikipedia

It is only simple arithmetic but it seems to me quite remarkable that the long journey from the dawn of anatomically modern humans (AMH) some 250,000 years ago, when considered along any particular line of descent, contains not more than some 12,000 individuals. So the right 12,000 names, if I knew them, would suffice to describe all the individuals on any specific line of descent from my origins as an anatomically modern human. Twelve thousand is not so great a number of people. It is less than the population of the little town I live in and it is a number that would be comfortably handled by even quite a small database. I even hear that some people boast more than 12,000 followers on Twitter and others have more than 12,000 “friends” on Facebook! It does not take many minutes to set up an Excel sheet with 12,000 line items, each line then representing one individual on one of my particular lines of descent.

So I have started a new blogsite called 6,000 Generations to provide an outlet for my speculations about individuals from my Ancestral Generations (AG’s).

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The need to communicate leads to the development of language

October 21, 2011

The origin of language was once a forbidden subject and in 1866, the Linguistic Society of Paris went so far as to ban debates on the subject – because it was considered too speculative to be a matter for serious people! But I find the question fascinating. When and how language developed remains a mystery. But with communication and language being such a clear measure of the distinction between humans and other primates, it seems obvious that there must be some genetic basis for this difference.

The “Language Gene” Turns Ten

Ten years ago this month, a team of University of Oxford scientists published a description of a family who struggled with words. By comparing their DNA, the scientists zeroed in for the first time on a gene associated with language, dubbed FOXP2.

Genetic evidence suggests that the basis of language appeared among hominids prior to the evolutionary split that gave rise to Homo neanderthalensis.  Having the genetic wherewithal for having language does not of course prove that hominids had language 400,000 years ago. But I would suggest that the need for a particular characteristic (whether for survival or merely for coping better with the prevailing environment) itself predisposes for those factors which enable the correct expression of the relevant genes to enhance the characteristic. And this leads to the role that epigenetics and the inheritance of factors controlling gene expression – rather than mutations of the genome – may have had in the development of language.

(more…)

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Humans prefer to cooperate, chimps don’t

October 18, 2011

Perhaps this was one of the critical genetic traits which – in evolutionary terms – helped humans  separate from the apes and power ahead to be the leading species on the planet.  It is not difficult to imagine that a “cooperation” gene or a “motivation to cooperate” gene – if such a thing exists – could have resulted in a number of “downstream” needs (for communication, language, artefacts, complex social organisations, arts and science) which in turn selected for and influenced the development of the traits which distinguish anatomically modern humans from other primates.

A new paper from the Max Planck Institutes in Leipzig and Nijmegen:

Yvonne Rekers, Daniel B.M. Haun and Michael Tomasello. Children, but Not Chimpanzees, Prefer to Collaborate. Current Biology, 2011 DOI: 10.1016/j.cub.2011.08.066

 Summary

Human societies are built on collaborative activities. Already from early childhood, human children are skillful and proficient collaborators. They recognize when they need help in solving a problem and actively recruit collaborators.

The societies of other primates are also to some degree cooperative. Chimpanzees, for example, engage in a variety of cooperative activities such as border patrols, group hunting, and intra- and intergroup coalitionary behavior. Recent studies have shown that chimpanzees possess many of the cognitive prerequisites necessary for human-like collaboration. Chimpanzees have been shown to recognize when they need help in solving a problem and to actively recruit good over bad collaborators. However, cognitive abilities might not be all that differs between chimpanzees and humans when it comes to cooperation. Another factor might be the motivation to engage in a cooperative activity. Here, we hypothesized that a key difference between human and chimpanzee collaboration—and so potentially a key mechanism in the evolution of human cooperation—is a simple preference for collaborating (versus acting alone) to obtain food. Our results supported this hypothesis, finding that whereas children strongly prefer to work together with another to obtain food, chimpanzees show no such preference.

Highlights

  • ► First study comparing collaborative motivation between children and chimpanzees
  • ► Children, but not chimpanzees, prefer collaborative over individual food acquisition
  • ► Motivation might be one key factor in the evolution of human-like cooperation

Science Daily: 

Researchers from the MPI for Evolutionary Anthropology in Leipzig and the MPI for Psycholinguistics in Nijmegen have now discovered that when all else is equal, human children prefer to work together in solving a problem, rather than solve it on their own. Chimpanzees, on the other hand, show no such preference according to a study of 3-year-old German kindergarteners and semi-free ranging chimpanzees, in which the children and chimps could choose between a collaborative and a non-collaboration problem-solving approach. ….

The research team presented 3-year-old German children and chimpanzees living in a Congo Republic sanctuary with a task that they could perform on their own or with a partner. Specifically, they could either pull two ends of a rope themselves in order to get a food reward or they could pull one end while a companion pulled the other. The task was carefully controlled to ensure there were no obvious incentives for the children or chimpanzees to choose one strategy over the other. “In such a highly controlled situation, children showed a preference to cooperate; chimpanzees did not,” Haun points out.

The children cooperated more than 78 percent of the time compared to about 58 percent for the chimpanzees. These statistics show that the children actively chose to work together, while chimps appeared to choose between their two options randomly. ….. Future work should compare cooperative motivation across primate species in an effort to reconstruct the evolutionary history of the trait. …..

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Acquired, hereditary epignetic codes could evolve faster than genetic mutations

October 3, 2011

Lamarckism  – after the French biologist Jean-Baptiste Lamarck (1744–1829) – is the idea that an organism can pass on characteristics that it has acquired during its lifetime to its offspring (soft inheritance). Publication of Charles Darwin’s theory of natural selection, and Mendelian genetics led to the general abandonment of the Lamarckian theory of evolution in biology. Despite this abandonment, interest in Lamarckism has recently increased, as several studies in the field of epigenetics have highlighted the possible inheritance of behavioral traits acquired by the previous generation.

Hard inheritance is the passing down of the constant nucleotide sequence of DNA which only changes by rare random mutation. The very slowness of this rate of mutation – and since mutations are usually not beneficial – has been a problem in explaining the variation and diversity observed in particular species. The variations observed in modern humans and which have presumably been generated within just the last 50,000 to 100, 000 years are difficult to explain by natural selection alone especially since there have only been some 5,000 generations available for this diversity to have been established.

A mechanism has long been sought for soft inheritance where environmental influences can be brought into play. Epigenetic mechanisms leave DNA sequence unaltered but can affect DNA by preventing the expression of genes.

A new paper in Science provides some further evidence that the epigenome may well be the hereditary “carrier” of environmental effects but may also cause much more rapid change than genetic mutations.

Science Daily: A “hidden” code linked to the DNA of plants allows them to develop and pass down new biological traits far more rapidly than previously thought, according to the findings of a groundbreaking study by researchers at the Salk Institute for Biological Studies. The study, published September 16 in the journal Science, provides the first evidence that an organism’s “epigenetic” code — an extra layer of biochemical instructions in DNA — can evolve more quickly than the genetic code and can strongly influence biological traits. ……..

…. Now that they have shown the extent to which spontaneous epigenetic mutations occur, the Salk researchers plan to unravel the biochemical mechanisms that allow these changes to arise and get passed from one generation to the next.

They also hope to explore how different environmental conditions, such as differences in temperature, might drive epigenetic change in the plants, or, conversely, whether epigenetic traits provide the plants with more flexibility in coping with environmental change.

“We think these epigenetic events might silence genes when they aren’t needed, then turned them back on when external conditions warrant,” Ecker said. “We won’t know how important these epimutations are until we measure the effect on plant traits, and we’re just now to the point where we can do these experiments. It’s very exciting.”

Read Article

R. J. Schmitz, M. D. Schultz, M. G. Lewsey, R. C. O’Malley, M. A. Urich, O. Libiger, N. J. Schork, J. R. Ecker.Transgenerational Epigenetic Instability Is a Source of Novel Methylation Variants. Science, 2011; DOI:10.1126/science.1212959

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New Scientist: Climate change led to the “golden age” of human evolution

August 8, 2011

The New Scientist has been one of the high priests of the AGW doctrine and “global warming” has been a dirty word. It represents politically correct “establishment science” and generally shuns the scepticism and irreverence of the true scientist. It has been – and still is – extremely reluctant to admit to any weaknesses in AGW dogma or in any possible benefits of global warming. But as “global warming” has morphed to the less emotive “climate change” and it is becoming clearer that man-made emissions don’t even control global CO2 levels – let alone the climate – the “settled science” is being shown to be anything but settled. There are some slight signs that the New Scientist is positioning itself so that it can be found to be on the side of the good guys no matter what surprises the climate may have in store.

Change and variability in Plio-Pleistocene climates: Modelling the hominin response by Matt Grove is a new paper in the Journal of Archaeological Science.

  • The research expands a technique originally developed by theoretical biologists.
  • The technique distinguishes between climatic change and climatic variability.
  • Change results in directional selection; variability selects for plasticity.
  • Results suggest selection for plasticity increases c.2.3-2.5 mya.
  • This date range coincides with the evolution of Homo and the spread of the Oldowan.

The New Scientist writes.

Thank climate change for the rise of humans 05 August 2011 by Andy Coghlan

SOME claim climate change will destroy our species; now it seems it also helped forge it. The rapid fluctuations in temperature that characterised the global climate between 2 and 3 million years ago coincided with a golden age in human evolution.

Australopithecus africanus

The fossil record shows that eight distinct species emerged from one hominin species, Australopithecus africanus, alive 2.7 million years ago. The first members of our genus appeared between 2.4 and 2.5 million years ago, while Homo erectus, the first hominin to leave Africa, had evolved by 1.8 million years ago.

To work out whether climate had a hand in the speciation spurt, Matt Grove of the University of Liverpool in the UK turned to a global temperature data set compiled by Lorraine Lisiecki at the University of California, Santa Barbara. Lisiecki analysed oxygen isotopes in the shells of fossilised marine organisms called foraminifera. During glacial periods, the forams’ shells contain more of the heavier of two oxygen isotopes, as the lighter one is preferentially accumulated in snow and ice rather than the ocean.

Grove found that the mean temperature changed suddenly on three occasions during the last 5 million years. Each change was equivalent to the difference between glacial and interglacial temperatures – but none of these episodes coincided with the hominin “golden age”. What marked out this period was a greater range of recorded temperatures, suggesting it was a time of rapid but short-lived fluctuations in climate. Grove says such conditions would have favoured the evolution of adaptability that is a hallmark of the genus Homo (Journal of Archaeological Science, DOI: 10.1016/j.jas.2011.07.002). Grove says the classic survival traits of H. erectus, forged during this period of change, include teeth suited for generalised diets and a large brain – both of which should have been advantageous at a time of swift climate change.

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Vladimir Nabokov vindicated – about butterflies

January 27, 2011
Polyommatus icarus 5

Polyommatus blue: Image via Wikipedia

Vladimir Nabokov (yes, he of Lolita fame) lived in Cambridge, Massachusets from 1942 to 1948 and while teaching at Wellesley he was curator of lepidoptery at Harvard University’s Museum of Comparative Zoology. His career in entomology was almost as distinguished – but not as lucrative – as his career in literature. In his spare time he composed chess problems. But his work in all these fields was characterised by his “love of detail and contemplation and symmetry”.

In 1945 he published a theory of butterfly evolution claiming that butterflies came to the New World in five waves of migration, through Asia across the Bering Strait into Alaska and then southward through North and then South America (much as humans migrated). Other butterfly experts scoffed at the idea. Nabokov’s theory was not taken seriously until after his death in 1977. Then, in the past decade, gene-sequencing technology finds that Nabokov was right all along and ironically during his life  “Nabokov never accepted that genetics or the counting of chromosomes could be a valid way to distinguish species of insects, and relied on the traditional (for lepidopterists) microscopic comparison of their genitalia”.

Now his theory stands vindicated by work  reported in a new paper in the Proceedings B of the Royal Society:

Phylogeny and palaeoecology of Polyommatus blue butterflies show Beringia was a climate-regulated gateway to the New World by Roger Vila, Charles D. Bell, Richard Macniven, Benjamin Goldman-Huertas, Richard H. Ree, Charles R. Marshall, Zsolt Bálint, Kurt Johnson, Dubi Benyamini and Naomi E. Pierce  doi:10.1098/rspb.2010.2213 Proc. R. Soc. B

Abstract: ….. By integrating molecular phylogeny, historical biogeography and palaeoecology, we test a bold hypothesis proposed by Vladimir Nabokov regarding the origin of Neotropical Polyommatus blue butterflies, and show that Beringia has served as a biological corridor for the dispersal of these insects from Asia into the New World. We present a novel method to estimate ancestral temperature tolerances using distribution range limits of extant organisms, and find that climatic conditions in Beringia acted as a decisive filter in determining which taxa crossed into the New World during five separate invasions over the past 11 Myr. Our results reveal a marked effect of the Miocene–Pleistocene global cooling, and demonstrate that palaeoclimatic conditions left a strong signal on the ecology of present-day taxa in the New World. …..

From Neatorama:

There were several plausible hypotheses for how the butterflies might have evolved. They might have evolved in the Amazon, with the rising Andes fragmenting their populations. If that were true, the species would be closely related to one another.

But that is not what Dr. Pierce found. Instead, she and her colleagues found that the New World species shared a common ancestor that lived about 10 million years ago. But many New World species were more closely related to Old World butterflies than to their neighbors. Dr. Pierce and her colleagues concluded that five waves of butterflies came from Asia to the New World — just as Nabokov had speculated.

“By God, he got every one right,” Dr. Pierce said. “I couldn’t get over it — I was blown away.”

Dr. Pierce and her colleagues also investigated Nabokov’s idea that the butterflies had come over the Bering Strait. The land surrounding the strait was relatively warm 10 million years ago, and has been chilling steadily ever since. Dr. Pierce and her colleagues found that the first lineage of Polyommatus blues that made the journey could survive a temperature range that matched the Bering climate of 10 million years ago. The lineages that came later are more cold-hardy, each with a temperature range matching the falling temperatures.


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Why body temperature is what it is – perhaps

December 28, 2010

American Society For MicrobiologyA new on-line paper in mBio hypothesises that mammalian body temperature is the result of an optimisation between a high enough temperature to ward of fungal species invading the body on the one hand and a low enough temperature on the other to minimise the quantity of fuel needed to support metabolism.

Mammalian Endothermy Optimally Restricts Fungi and Metabolic Costs

by Aviv Bergman and Arturo Casadevall

Albert Einstein College of Medicine

In this study the researchers hypothesis was tested by modeling the fitness increase with temperature versus its metabolic costs.  They analysed the tradeoff involved between the costs of the excess metabolic rates required to maintain a body temperature and the benefit gained by creating a thermal exclusion zone that protects against environmental microbes such as fungi. Their result yielded an optimum at 36.7°C, which closely approximates mammalian body temperatures. The commonly accepted average core body temperature (taken internally) is 37.0 °C (98.6 °F).

Authors Abstract: Endothermy and homeothermy are mammalian characteristics whose evolutionary origins are poorly understood. Given that fungal species rapidly lose their capacity for growth above ambient temperatures, we have proposed that mammalian endothermy enhances fitness by creating exclusionary thermal zones that protect against fungal disease. According to this view, the relative paucity of invasive fungal diseases in immunologically intact mammals relative to other infectious diseases would reflect an inability of most fungal species to establish themselves in a mammalian host. In this study, that hypothesis was tested by modeling the fitness increase with temperature versus its metabolic costs. We analyzed the tradeoff involved between the costs of the excess metabolic rates required to maintain a body temperature and the benefit gained by creating a thermal exclusion zone that protects against environmental microbes such as fungi. The result yields an optimum at 36.7°C, which closely approximates mammalian body temperatures. This calculation is consistent with and supportive of the notion that an intrinsic thermally based resistance against fungal diseases could have contributed to the success of mammals in the Tertiary relative to that of other vertebrates.

Mammals are characterized by both maintaining and closely regulating high body temperatures, processes that are known as endothermy and homeothermy, respectively. The mammalian lifestyle is energy intensive and costly. The evolutionary mechanisms responsible for the emergence and success of these mammalian characteristics are not understood. This work suggests that high mammalian temperatures represent optima in the tradeoff between metabolic costs and the increased fitness that comes with resistance to fungal diseases.

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Paraguay suspends Natural History Museum’s “genocide” expedition

November 16, 2010
Very approximate location of the Gran Chaco (U...

Gran Chaco area: Image via Wikipedia

I posted a few days ago about the dangers of the Natural History Museum’s planned 60 – 100 strong “expedition” to the forests of Paraguay.

Today comes news that on Monday Paraguay suspended a British scientific expedition into the remote Chaco woodlands after indigenous rights groups raised concerns over the welfare of protected tribes in the region.

Sponsored by Britain’s Natural History Museum, the 45-member British-Paraguayan expedition planned to conduct a month-long survey of animal and plant life in the sprawling savanna 800 kilometers (500 miles) north of Asuncion, the ministry said in a statement.

The decision to suspend it followed “last minute” concerns raised by indigenous rights groups including Iniciativa Amotocodie, and recommendations by the Washington-based Inter-American Human Rights Commission, the environment ministry said.

“The massive presence of about 60 researchers in the land inhabited by the Ayoreo tribal groups in the remote, northern reaches of Chaco… poses significant risks to their lives and territory,” Amotocodie said in a statement.

The rights groups argued that since the tribes have had very little contact with the outside world they are at risk of contracting diseases that in some cases could prove fatal.

It would have been far better if the Natural History Museum had itself suspended the expedition and had taken the initiative to carry out the consultations which it is now forced to conduct.

Seattle pi:

Paraguay denied authorization Monday for a British-led scientific expedition to catalog plants and animals in the country’s remote northern corner, saying there isn’t enough time to consult with relatives of nomadic Indians who try to remain isolated as they pass through the area.

The non-governmental Amotocoide Initiative, an advocacy group for native Ayoreo Indians who live in the dry forests of northern Paraguay, had warned that scientists might carry European diseases to the Indians, leave trash or otherwise suffer violent encounters.

Isabel Basualdo, director of the biodiversity office of Paraguay’s environmental ministry, said in a statement that the decision follows the recommendation of the Interamerican Human Rights Commission that public hearings and all other legal requirements are complied with before such a visit.

Richard Lane, the British Natural History museum’s director of science, said the expedition had been suspended while consultations take place. “We believe that this expedition to scientifically record the richness and diversity of the animals and plants in this remote region is extremely important for the future management of this fragile habitat,” Lane said in a statement.

But some anthropologists who advocate for the Ayoreos say no outsiders should enter these dry forests, where small bands of people are still trying to live in isolation from the modern world. Irene Gauto, who represents the private environmental group Guyra Paraguay, told The Associated Press that the environment ministry “sent a letter to the British museum arguing that, for now, it’s better to delay the visit of the scientists because there hasn’t been time enough to hold public hearings with the relatives of the forest-dwelling Ayoreos,” one of 20 surviving indigenous groups living in Paraguay.

The trip was to begin Saturday to the Chovoreca and Cabrera-Timane hills near Paraguay’s border with Bolivia and Brazil, about 500 miles (800 kilometers) northeast of the capital. The scientists planned to catalog species on a private cattle ranch within a Paraguayan nature reserve. The ranch’s owners approved the trip and said indigenous people didn’t live there, Gauto said.

The government appeared ready to approve the trip. But the situation changed after a leader of the Totobiegosode subgroup of Ayoreos, Chiri Etacori, said about two dozen nomadic Ayoreos wander through the area.

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