Thursday, 30 August 2007

A spin around the blogosphere this week…

You may remember Darren Naish’s post on wolf-hunting eagles. Well Darren has recently posted a video on his blog in which an unfortunate young deer gets killed by big bad eagle.

Also, Carl Zimmer has created a photo album of geeky scientific tattoos and you can even explore even more at Street Anatomy.

And don't forget that Fish Feet will be hosting the Oekologie blog carnival in September.

Monday, 20 August 2007

Why does my baby have a tail?

As I’m having a baby my mind has recently been turned to thoughts of the very weird and wonderful world of developmental biology. As a new parents tracks the progress of their child, you can’t help wonder about some of the really bizarre stages it goes through.

Some of the odd developments (gill slits and tails as examples) can be explained by the research of a 19/20th century German researcher, Ernst Haeckel. This eminent man was more than a scientist, he was a, physician, philosopher, artist and teacher. Haeckel’s contribution to biology was immense, in addition to naming and identifying thousands of new species (one his beautiful colour plates is displayed on the right), he contributed many large-scale concepts to the fields of ecology and biology. His most controversial theory is often referred to as Recapitulation Theory.

This theory is often stated as "Ontogeny recapitulates phylogeny", simply meaning that as an organism develops, it replays its evolutionary history. His theory is closely tied to the figure below (redrawn by Romanes in 1892), which shows striking similarities in the various stages of development of some vertebrates. We now know that Haeckel, perhaps in an attempt to bolster his theory or perhaps because his specimens were incomplete, embellished the drawings to some degree; so these examples must be taken with a grain of salt but hey are correct in a generalized sense. Haeckel, a great believer in the works of Charles Darwin, used this illustration and many of his other drawings to support the theory of evolution and argued that as an individual develops, it repeats the full evolutionary development of its species.
Now strictly speaking, Haeckel wasn’t exactly right, and a developmental biologist would set you straight about exactly how wrong Haeckel was, but I’m not going to be debating this point because no modern biologist would taken his theory to be literally true. What I would like to focus on is the broader picture that Haeckel’s observations support. We are all fundamentally related and simply, those of us that share a closer common ancestor will look more alike. So it is not a surprise that we resemble other mammals more closely than we resemble a fish, frog or reptile. Also, evolutionary steps are often like ‘additions’, adding new features to the developing form, so again it is not a surprise that our own human embryos go through stages resembling that of other animals.

If Haeckel were to be taken literally, at some point a growing human embryo would be a viable fish, amphibian, reptile, or early primate. But in fact a human embryo can only ever be a human. The commonalities we share with other animals that Haeckel discovered are indicative of our common ancestry and his theory helps us understand that stages in our embryonic development reflect these connections. Some of the weird things human embryos go through include:

• Early on the embryo develops gill slits (more correctly called pharyngeal arches) in its neck. In a human, the first gill bar (which supports the pharyngeal arch) develops into the lower jaw as well as the ear bones (malleus and the stapes). The gill slits will then close, leaving just one open for the development of the ear opening

• By the fourth week a clear tail is seen in the human embryo. It recedes after a few weeks and these tissues form what is commonly known as the tailbone (coccyx).

• Around the fifth month of gestation the embryo develops lanugo, a fine, downy hair, which covers its entire body. It provides some insulation, as the child has little in the way of fat reserves. This hair is usually lost by birth, though is often seen on premature infants.

Tuesday, 14 August 2007

Tangled Bank #86

Welcome to Fish Feet, host of the 86th Tangled Bank blog carnival!

The Scientific Process
• Kevin of The Other 95% discusses metrics of scientific advancement and their impact on progress.

• Sunil at Balancing Life gives readers invaluable advice on writing grant proposals.

• Christian of Med Journal Watch writes about the artificial settings of diet trials and the value of their findings.

• Shalini at Scientia Natura debates the impact of a recent palaeoanthropological discovery on the theory of evolution?

• CAD of VWXYNot? describes how the progression of tumorigenesis mirrors the process of evolution by natural selection.

• Eric of The Primate Diaries discusses offspring abandonment in the ancient and natural world.

• Jeremy at The Voltage Gate contributes a riveting article on the ecology of fear in Yellowstone National Park.

• Scott of Dammit Jim! I’m a biologist not a… posts a cool youtube video and explores the curious mating rituals of jumping spiders.

• Mike at 10,000 Birds explores the diversity of Waxwings.

Agriculture and Environment
Matthew of Behavioral Ecology muses about how even parasite-resistant sheep avoid eating shit!

Jeremy of Agricultural Biodiversity Weblog discusses variation in the glycaemic index of various crops.

• Emmett from The Natural Patriot shares his perspective on the writing and philosophy of author and environmentalist, Richard Louv.

• Martin of Aardvarchaeology reviews Alan Weisman’s book, the The World Without Us

Human Biology, Diet and Medicine
• Paddy of Swedish Extravaganza writes a balanced discussion on the ethical aspects of vegetarianism.

• Cathy of Lab Cat talks about pre and probiotics.

• GrrlScientist of Living the Scientific Life talks about a bone hormone, which is linked to obesity and Type 2 Diabetes.

• Alvaro of Sharp Brains has submitted a podcast interview with neuropsychologist Dr. Elkhonon Goldberg who talks about brain improvement research.

• FitBuff of Total Mind and Body Fitness reports on a recent study which examines the unconscious signals we use to find Mr. or Mrs. Right!

• Hsien of Eye on DNA imagines the possibility of genome sequencing being available to the public.

• Lev at Ouroboros writes an article about protein abundance in long-lived worm mutants.

• Jeremy at Another Blasted Weblog discusses restriction endonucleases, the molecular scissors that allow biologists to cut DNA.

I’m glad to have hosted the carnival and have enjoyed reading all of the great submissions! Two weeks from now on August 29, visit Tangled Bank again at Balancing Life.

Sunday, 12 August 2007

Long Absence

Sorry I have been absent for so long. Life has been getting pretty busy, with grad school and a new baby on the way. But I hope to be back to blogging (at least once a week, if not more often) and Tangled Bank has given me the kick in the pants I need to get back to it! Visit us on August 15 to check Tangled Bank #86!