Transitionals are a hot topic in evolutionary biology because they provide clear evidence of common ancestry. In linking two seemingly unrelated groups in a shared genetic heritage one looks for evidence of organisms that display a moasic of characteristics, some characters defining one group and some another. Transitional forms are those organisms that display this mix of traits from two seemingly desperate groups. Contrary to denials of creationists transitionals are indeed found throughout the fossil record.
The evolutionary transition from land mammals to cetaceans (whales, porpoises and dolphins) is one of these well documented transitions. For many years the origin of whales was a mystery. Whales were obviously mammals but where they fit in the mammal family tree was unknown. Comparing the genes of cetaceans and other mammals lead to the conclusion that cetaceans arose from within a group of hoofed mammals called artiodactyls, but, this conclusion disagreed with the fossil evidence. This disagreement largely ended in 2001 when University of Michigan paleontologist Phillip Gingerich and colleagues published an account of new species of proto-whales from Pakistan, Artiocetus clavis and Rodhocetus balochistanensis. These fossils had skulls with the characteristic features of whales but unlike modern whales had hind limbs. But these early whales, protocetids, didn't just have any hind limbs but hind limbs with ankle bones only found in the artiodactyls, exactly as the genetic data predicted.
Gingerich and colleagues describe another protocetid from Pakistan in the journal Public Library of Science ONE. The two new fossils are typical of early whales with four well-developed limbs and a cetacean-like skull.
Human populations vary genetically, however, much of this variation is not divided into discrete groups but rather is distributed as a cline, or gradually, with one population smoothly transitioning into another. Genetic isolation in most human populations is therefore primarily dictated by distance. Also, the human propensity for roaming and spreading into new environments means that humans spread their genes widely and tend to genetically homogenize populations. However, there are some exceptions to these general patterns. Some human populations have experienced relatively long periods of genetic isolation.
Pygmies of West and Central Africa are known for their comparatively short stature. Pygmies do not comprise a single group but rather approximately two dozen groups with a diverse array of different languages. While on average adult male height is about 5 feet, comparatively small for most human populations, mean height can vary by as much as 8 inches among different pygmy groups. Pygmies are among the last groups in Sub-Saharan Africa to practice the hunter-gatherer lifestyle typical of our earliest human ancestors and as such understanding their evolutionary history can provide important clues to the history and diversification of our species.
The American Recovery and Reinvestment Act, otherwise known as the Economic Stimulus bill, includes 2.5 billion in additional funds for the National Science Foundation (NSF) specifically for "research and related activities". To help build scientific infrastructure 300 million of these funds are reserved for the NSF's Major Research Instrumentation program. An additional 502 million, of which 400 million will go to research equipment and facilities and 100 million to education and human resources, will go to other NSF activities. Incidentally NSF's Major Research Instrumentation program provided funds for Cincinnati Museum Center's (CMC) new Molecular Ecology and Systematics Laboratory. Hopes are this will push the US towards increased innovation in basic science. New proposals to the NSF, if funded, will help CMC grow as a research institution, spread scientific literacy and train students at every level in the high tech skills required for a modern economy. Wish me luck!
Today is the 200th anniversary of Charles Darwin's birth. The notion that life changes over time and the idea that species share a common ancestry both predate Darwin, but, Darwin was the first to provide a viable mechanism by which biological evolution occurs, namely evolution by natural selection. Darwin solidified the idea of evolution and this idea rapidly spread in acceptance among scientists after the publication of Origin of Species.
Evolution's importance can not be overstated. Today evolution is the central organizing principle in the life sciences. To date, it is our only viable explanation for the diversity of life on earth. Data from paleontology, ecology, anatomy and most recently, modern molecular genetics and comparative genomics continue to support the conclusion that life shares a common genetic heritage.
Darwin is a model of how science should work and how scientists should conduct themselves. He was careful, thorough, curious, and dedicated to the details and all the while humble and considerate of his colleagues. Darwin did not have the computational mind of a Newton nor was he capable of the abstraction of an Einstein. Darwin's genius was simply as a clear thinker, ever mindful of the evidence and ready to follow that evidence where it leads. At the center of Darwin's ideas was a broad knowledge of natural history all to be brought to bear on big questions in science.
Darwin and Abraham Lincoln were born on exactly the same day. Both played key roles in building the world we live in today. The bicentenial of their births should be a time to reflect on their accomplishments and follow their example to move society forward.
Happy birthday Chuck!
With 2009 as the 200th anniversary of Darwin's birth and the 150th anniversary the publication of the Origin of Species evolution is spreading across the web faster than a large bill in a drought-ridden finch population. The American Association for the Advancement of Science's Science Magazine has a new blog all about origins. Inspired by Darwin, AAAS will spread news on all things evolution from anthropology to genomics to the origin of life. So check in regularly as part of Darwin year 2009!
Cincinnati Museum Center's Union Terminal opened the rotunda to the community to watch the inauguration of Barack Obama as the 44th President of the United States. Hundreds of people from Cincinnati/Northern Kentucky area were in attendance to watch this milestone in American history. Thanks to the outgoing Bush administration and good luck to the new Obama administration!
Chicago's Field Museum of Natural History will cut it's budget by 15%. The Field is not only among the top museums in the country but a center of research excellence in the biological sciences. In an article in Nature News Field Museum associate curator and ornithologist Shannon Hackett worries that severe cuts could jeopardize the museum's stature as a leading research center. Hackett comments, "Once you lose your academic stature, it is very difficult to regain". A major problem lies in loses in the museum's endowment dropping from $320 million in the spring to $215 million in November. Museums around the country are experiencing similar problems. Especially hard hit are those institutions that receive state funding in those states with falling tax revenues. The University of Pennsylvania's Museum of Archaeology and Anthropology has cut 18 research positions and the Virginia Museum of Natural History announced in October that the state has ordered a 10% budget cut resulting in job losses and a reduction in hours the museum is available to the public.
Clearly it is as important now as ever to support your local natural history museum. Visit your museum regularly, consider a membership and if you have the means, donate, so that these vital centers of scientific research and education can continue to grow and thrive. The long term economic health of the US is critically linked to a scientifically literate society where discovery and innovation spawns economic opportunity. Natural history museums are key players in building the scientific literacy required in any successful modern economy.
In the December 12 issue of the journal Science Ros Clubb of the Royal Society for the Protection of Animals and colleagues, including well known elephant researcher Cynthia Moss, report that captive elephants do not live as long as their free-living counterparts, or even as long as working elephants in Burmese timber camps.
Collecting data from over 4,500 elephants from European Zoos, wild populations in Amboseli National Park in Kenya and working elephants in Burmese logging camps, the authors found a significant correlation between captivity and longevity. Females from a well studied population of African Savannah Elephants (Loxodonta africana) in Amboseli National Park in Kenya exhibited a median life span of 56.0 years (these data excluded mortality from humans). African Savannah Elephants in zoos have a median life span of only 16.9 years. As of 2005 when the study ended female African Savannah Elephants in captivity experienced a mortality risk 2.8 times higher than the natural mortality of wild female elephants in Amboseli. Captive-born female African Savannah Elephants die earlier in zoos than in the wild but infant and juvenile mortality was similar between wild and captive elephants.
For Asian Elephants (Elephas maximus) the effect of zoo captivity on mortality was also significant. Captive female Asian Elephants in the study exhibited a median life span of 18.9 years while working Asian Elephants in a Burmese timber operation had a median life span of 41.7 years. While mortality risk in African Savannah Elephants went down over time, suggesting improved captive management, there was no significant reduction in mortality for Asian Elephants. Also, being born in a zoo versus born in the wild had a significant effect on surviorship in Asian Elephants. Ironically, wild-caught Asian Elephants did better in captivity than their captive-born counterparts.
Elephants live in tightly knit social groups of females and juveniles with very long-term associations among individuals. Wild female elephants rarely move between groups, but, zoos regularly transfer individuals among institutions. Female Asian Elephants are moved around among European Zoos approximately once every 7-years. Transfers have an effect on the health of captive elephants. This study found that inter-zoo transfers significantly reduced survivorship in Asian Elephants.
Georgia Mason, a co-author on this study and zoologist at the University of Guelph in Ontario, Canada, discussed the results on the December 12 Science Magazine podcast. According to Mason the situation for American zoo elephants is no better than their European counterparts. 15% of zoo-born elephants in Europe die in their first year while in the USA 40% of zoo-born elephants die before the age of one.
Small group size, frequent inter-zoo transfers, and comparatively tiny enclosures for an animal that has orders magnitude greater home range area in the wild are all likely contributors to the problem of reduced survivorship in zoo elephants. However, solutions to this problem are not straightforward. Large sums of money have been spent in European and US zoos to build larger enclosures for captive elephants but the study by Clubb and colleagues found little evidence that such improvements have resulted in increased survivorship in captive elephants. Some increases in survivorship for African Savannah Elephants have occurred but not nearly enough to bring their surviorship on par with wild counterparts and the study found that despite increased spending and larger enclosures there was no increase in survivorship for Asian Elephants. Mason in the Science Podcast interview pointed out that recent expenditures of approximately 23 million US dollars spent on improving enclosures for the elephants at the Oklahoma City Zoo were greater than the entire annual budget for the Kenya Wildlife Service or the South African National Parks Authority. Perhaps the greatest concern is that captive elephant populations are not self sustaining and can not survive without introduction of individuals taken from the wild.
This study provides a compelling argument for an elevated discussion on not just captive elephants but the welfare of other large-ranging, social mammals as well. Hopefully this study will place a renewed emphasis on future research and novel approaches to captive husbandry of these magnificent mammals.
Clubb, R., Rowcliffe, M., Lee, P., Mar, K. U., Moss, C., Mason, G. J. (2008). Compromised Survivorship in Zoo Elephants Science, 322 (5908) DOI: 10.1126/science.1164298