Making choices to conserve the world's species: what, where and when?

Chair: Sir John Lawton CBE FRS

Speakers: Professor Georgina Mace FRS, Dr Jonathan Baillie, Professor Hugh Possingham and Dr Mark Avery

Conserving species is becoming more urgent as the pressures on natural areas intensify. There are increasing numbers of threatened species facing different problems in habitats all over the world. Unfortunately, there are many more problems than can be solved with the limited resources available to conservation bodies. So how do conservation biologists go about choosing what to focus on first, or where to invest most conservation funding?

There are both scientific and personal answers to this question. Scientifically-based methods can help to optimally allocate resources given a clearly stated desired endpoint or goal. But there are several alternative kinds of possible goals for species conservation that are not necessarily convergent. This meeting will bring together conservation science professionals from a range of organizations to debate the issues and see if there can be a shared species conservation science.

Proceedings were be chaired by Professor Sir John Lawton CBE FRS, currently Chairman of the Royal Commission on Environmental Pollution, and between 1999 and 2005 was Chief Executive of the Natural Environment Research Council. He trained as a zoologist in Durham, and has held posts at Oxford, York and Imperial College.

Other panel members include:

Professor Georgina Mace FRS is currently the Director of the NERC Centre for Population Biology at Imperial College London where she is also professor of Conservation Science. Previously she was Director of Science at the Institute of Zoology, Zoological Society of London. Her research interests focus on species extinction, the assessment of biodiversity change, biodiversity indicators and the consequences of biodiversity loss for people and environmental processes generally.

Dr Jonathan Baillie is Director of Conservation Programmes at the Zoological Society of London where he oversees field projects in over 50 countries worldwide. Jonathan has played a leading role in the development of global biodiversity indicators including the IUCN Sampled Red List Index, WWF Living Planet Index and WCS/ZSL Wildlife Picture Index.

Dr Mark Avery is the Conservation Director of the RSPB - a conservation charity with more than a million members - and is responsible for the Society's conservation policy and practice.

Profressor Hugh Possingham is Head of the Ecology Centre at the University of Queensland, Australia. He sits on 16 different advisory boards for government and non-government groups and is actively involved in policy.  Work from his lab helped stop land clearing in Queensland and New South Wales securing 1 billion tones of CO2.

Bengal Tiger Panthera tigris tigris

Tigers are the largest members of the cat family and are renowned for their power and strength.

There were eight tiger subspecies at one time, but three became extinct during the 20th century. Over the last 100 years, hunting and forest destruction have reduced tiger populations from hundreds of thousands of animals to perhaps fewer than 2,500. Tigers are hunted as trophies, and also for body parts that are used in traditional Chinese medicine. All five remaining tiger subspecies are endangered, and many protection programs are in place.

Bengal tigers live in India and are sometimes called Indian tigers. They are the most common tiger and number about half of all wild tigers. Over many centuries they have become an important part of Indian tradition and lore.

Tigers live alone and aggressively scent-mark large territories to keep their rivals away. They are powerful nocturnal hunters that travel many miles to find buffalo, deer, wild pigs, and other large mammals. Tigers use their distinctive coats as camouflage (no two have exactly the same stripes). They lie in wait and creep close enough to attack their victims with a quick spring and a fatal pounce. A hungry tiger can eat as much as 60 pounds (27 kilograms) in one night, though they usually eat less.

Despite their fearsome reputation, most tigers avoid humans; however, a few do become dangerous maneaters. These animals are often sick and unable to hunt normally, or live in an area where their traditional prey has vanished.

Females give birth to litters of two to six cubs, which they raise with little or no help from the male. Cubs cannot hunt until they are 18 months old and remain with their mothers for two to three years, when they disperse to find their own territory.

Studies slow the human DNA clock

Revised estimates of mutation rates bring genetic accounts of human prehistory into line with archaeological data.

·         Ewen Callaway

18 September 2012

At 500,000 years, the dating of this skull of Homo heidelbergensis clashed with previous DNA dates for Neanderthal origins.

J. TRUEBA/MSF/SPL

Article tools

The story of human ancestors used to be writ only in bones and tools, but since the 1960s DNA has given its own version of events. Some results were revelatory, such as when DNA studies showed that all modern humans descended from ancestors who lived in Africa more than 100,000 years ago. Others were baffling, suggesting that key events in human evolution happened at times that flatly contradicted the archaeology.

Now archaeologists and geneticists are beginning to tell the same story, thanks to improved estimates of DNA’s mutation rate — the molecular clock that underpins genetic dating^1–4. “It’s incredibly vindicating to finally have some reconciliation between genetics and archaeology,” says Jeff Rose, an archaeologist at the University of Birmingham, UK. Archaeologists and geneticists may now be able to tackle nuanced questions about human history with greater confidence in one another’s data. “They do have to agree,” says Aylwyn Scally, an evolutionary genomicist at the Wellcome Trust Sanger Institute in Hinxton, UK. “There was a real story.”

The concept of a DNA clock is simple: the number of DNA letter differences between the sequences of two species indicates how much time has elapsed since their last common ancestor was alive. But for estimates to be correct, geneticists need one crucial piece of information: the pace at which DNA letters change.

Geneticists have previously estimated mutation rates by comparing the human genome with the sequences of other primates. On the basis of species-divergence dates gleaned — ironically — from fossil evidence, they concluded that in human DNA, each letter mutates once every billion years. “It’s a suspiciously round number,” says Linda Vigilant, a molecular anthropologist at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. The suspicion turned out to be justified.

In the past few years, geneticists have been able to watch the molecular clock in action, by sequencing whole genomes from dozens of families⁵ and comparing mutations in parents and children. These studies show that the clock ticks at perhaps half the rate of previous estimates, says Scally.

In a review published on 11 September¹,Scally and his colleague Richard Durbin used the slower rates to reevaluate the timing of key splits in human evolution. “If the mutation rate is halved, then all the dates you estimate double,” says Scally. “That seems like quite a radical change.” Yet the latest molecular dates mesh much better with key archaeological dates.

Take the 400,000–600,000-year-old Sima de Los Huesos site in Atapuerca, Spain, which yielded bones attributed to Homo heidelbergensis, the direct ancestors of Neanderthals. Genetic studies have suggested that earlier ancestors of Neanderthals split from the branch leading to modern humans much more recently, just 270,000–435,000 years ago. A slowed molecular clock pushes this back to a more comfortable 600,000 years ago (see ‘Better agreement over the human story’).

SOURCE: REF. 1

A slower molecular clock could also force scientists to re-think the timing of later turning points in prehistory, including the migration of modern humans out of Africa. Genetic studies of humans around the world have suggested that the ancestors of Europeans and Asians left Africa about 60,000 years ago. That date caused many to conclude that 100,000-year-old human fossils discovered in Israel represented a dead-end migration rather than the beginning of a global exodus, says Scally. Scally’s calculations put “out of Africa” closer to 120,000 years ago, suggesting that the Israeli sites represent a launching pad for the spread of humans into Asia and Europe.

The latest genetic dates also fit with several sites in the Middle East that contain tools apparently made by modern humans but dating to around 100,000 years ago. At that time, sea levels between Africa and the Arabian Peninsula were lower than they are now, and a wetter climate would have made the peninsula lush and habitable, perhaps beckoning modern humans out of Africa. Rose, who works one such site, in Oman, says that he “has been over the moon” since reading Scally and Durbin’s paper.

The revised molecular clock may also help to settle a debate over whether humans ventured further into Asia more than 60,000 years ago, says Michael Petraglia, an archaeologist at the University of Oxford, UK, who favours an early date.

Although a slowed molecular clock may harmonize the story of human evolution, it does strange things when applied further back in time, says David Reich, an evolutionary geneticist at Harvard Medical School in Boston, Massachusetts. “You can’t have it both ways.”

For instance, the slowest proposed mutation rate puts the common ancestor of humans and orang-utans at 40 million years ago, he says: more than 20 million years before dates derived from abundant fossil evidence. This very slow clock has the common ancestor of monkeys and humans co-existing with the last dinosaurs. “It gets very complicated,” deadpans Reich.

Some researchers, including Scally, have proposed that the mutation rate may have slowed over the past 15 million years, thereby accounting for such discrepancies. Fossil evidence suggests that ancestral apes were smaller than living ones, and small animals tend to reproduce more quickly, speeding the mutation rate.

Little concrete evidence supports this idea, says Reich. He agrees that the molecular clock must be slower than was thought, but says that the question is how slow. “My strong view right now is that the true value of the human mutation rate is an open question.”