01/11/2009

About the Z-Letter

This blog is an on-line version of  the Z-Letter, an electronic newsletter on all things zoological, produced by Matthew Cobb of the University of Manchester. Be sure to contribute by commenting on the posts.

The newsletter contains brief items with links to articles, videos and sound files seen on the web, and anyone can receive it – simply send a mail to cobb at manchester dot ac dot uk

The header shows pronghorn antelope in Idaho. (c) WCS/W.B.Karesh.

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05/03/2010

SLOW-MO DOG EYE-MOUTH COORDINATION

This video is an advert for dog food, but nevertheless shows how dogs manage to leap to catch food. The neuronal processing is in fact remarkably complex: pattern recognition (it’s a treat), measurement of velocity and parabolic trajectory, computation of appropriate power needed, and its distribution, to get body to right place at the right time, opening of mouth, closing of mouth, landing with appropriate weight distribution. That’s just a description of the processes that must be taking place. How EXACTLY do they do it? No one knows…

02/03/2010

FOSSIL SNAKE ATE DINOSAUR BABIES

An article just published in PLoS Biology (open access) describes a fossil from Gujurat in India, from around 68 MY ago. Amazingly, the rock contains the remains of a 3.5 m long snake, coiled in a sauropod nest, complete with eggs and a sauropod nestling. On the basis of this fossil, and others found nearby, the authors (led by Jeffrey Wilson of the University of Michigan) conclude that the snake (never before described), Sanajeh indicus, preyed on newly-hatched dinosaurs. There’s a very cute reconstruction of the scene, in an accompanying (and very interesting) article by Michael Benton about the difficulties of reconstructing function and behaviour from fossils.

Figure 1. Fossil snake preserved within a sauropod dinosaur nesting ground. Beginning from the center of the lower portion of the photograph, the articulated skeleton of the snake Sanajeh indicus is coiled in a clockwise fashion around a crushed Megaloolithus egg (egg 3, at the junction of three blocks), with its skull resting on the topmost loop of the coil. The uncrushed Megaloolithus egg (egg 1) at right pertains to the same clutch, which would have contained six to 12 eggs. A second uncrushed Megaloolithus egg (egg 2) from the same clutch is still at the site. At lower right are the front quarters of a titanosaur hatchling, including elements of the thorax, shoulder girdle, and forelimb preserved in anatomical articulation. The titanosaur hatchling was approximately 0.5 m long, or one-seventh the length of Sanajeh (3.5 m long). No other sauropod bones were found at the site. Scale bar equals 5 cm.

Interpretive map of blocks shown in Figure 1.

Here’s the reconstruction, sculpture by Tyler Keillor and original photography by Ximena Erickson; image modified by Bonnie Miljour. (NB we’re looking at the scene from the other side of the images above).

The scales and patterning of the snake's skin is based on modern macrostomatan snakes, relatives of the fossil form. The hatchling dinosaur is reconstructed from known skeletal materials, but its color is conjectural. The eggs are based directly on the fossils. Taken from PLoS Biology.

01/03/2010

NAME THAT ANIMAL!

Not quite as simple as it might seem. Yes, that’s a cow. But what is it doing and why? NO GOOGLING!  And no it hasn’t been photoshopped.

23/02/2010

NAME THAT ANIMAL!

What kind of bird is this, and why is it special?

22/02/2010

HOW WE GOT WHERE WE ARE

An excellent resource in the latest issue of Current Biology seven reviews on the global genetic history of Homo sapiens, all available FREE. Not all the articles are easy going for the non-specialist, and lay readers might wish to focus on the introductory and concluding paragraphs, but this must surely be the most authoritative publicly available resource on the topic.

The issue opens with a guest editorial by archaeologist Colin Renfrew, summarising the “new synthesis” of genetic, linguistic and archaeological studies that are used to understand the history of our species. Genetics has shown clearly that we did indeed come “out of Africa”, around 70,000 years ago:

A study of 121 ethnically diverse African populations indicated the presence of 14 genetically distinct ancestral population clusters in Africa. Anatomically modern humans evolved in Africa around 200,000 yeas ago, migrated to Eurasia within the last 40000–80000 years and then migrated to the Americas within the last 15000–30000 years. The geographic expansion from Africa is thought to have been accompanied by a population bottleneck and a concomitant loss of genetic diversity. The migration of populations across the globe occurred in many small steps, with each migration event involving a sampling of variation from the previous population. In this figure, decreasing intensity of color represents the concomitant loss of genetic diversity as populations migrated in an eastward direction from Africa. Solid horizontal lines indicate gene-flow between ancestral human populations and the dashed horizontal line indicates recent gene-flow between Asian and Australian/Melanesian populations. (Taken from Current Biology)

Genetics can also show us how we colonised Europe:

This schematic map depicts major migratory events thought to have affected the gene pool of modern Europeans. Black arrows indicate the first settlement by modern humans around 45 thousand years ago (kya). At the end of the last ice age, around 10–15 kya, Europe was re-populated from glacial refugia (red arrows). Around 8–10 kya, Neolithic farmers came to Europe from Anatolia and the Fertile Crescent (green arrows). (Figure by Alessandro Achilli and Antonio Torroni.) Taken from Current Biology.

However, for the moment genetics is less able to resolve issues to do with the last 15-10,000 years, once we had become sedentary. For example, Renfrew writes:

“From a linguistic point of view, it is widely supposed that Proto-Indo-European or early Indo-European language, which is ancestral to Vedic Sanskrit and to most of the languages of North India and Pakistan (but not the Dravidian languages of the south), must have come to the sub-continent during the second millennium BC, presumably associated with some incoming population. But, even leaving linguistic issues aside, molecular genetic indicators for these migrations have not been very clearly identified”

To understand our more recent past, we not only need more data – for example from ancient DNA extracted from bones – we also need to develop new computational tools to be able to model the effects of migration and other changes on genetic and linguistic diversity in human populations. And above all we need to be able to confront these hypotheses with more reliable and unambiguous archaeological data. But for anyone interested in the history of our species, these are exciting times.

16/02/2010

NAME THAT ANIMAL!

What is this insect, what order does it belong to, and what does it use that snout thing for?

08/02/2010

THE SPARROWHAWK OF STOPFORD

As seen by Dr Liz Sheffield from her office window, looking onto the back quad of the Stopford Building at the University of Manchester. One of our resident sparrowhawks with its lunch. Look at that eye! Thanks to Laura for alerting us to the kill, and photocredit goes to Tony Bentley from the Photographics Unit. Let’s hope the sparrowhawks breed again this year.

07/02/2010

ANOTHER COLOURED DINOSAUR – SO WHAT?

A couple of weeks ago I described the report in Nature that suggested it was possible to determine what colour feathered dinosaurs were. Now there’s a report in Science magazine – not yet published – that does the same trick, with a different dino. Jerry Coyne has blogged on this over at Whyevolutionistrue.com. The beast in question is Anchiornis huxleyi, a small (woodpecker-sized) feathered but non-flying dinosaur from about 150 million years ago. It looks cute:

Reconstruction of the plumage color of  Anchiornis huxleyi.   Color plate by Michael A. Digiorgio, from Science.

The authors say that because it was a non-flying dinosaur, these striking feathers suggest that colouration (and hence signalling or camouflage) may have been as important as aerodynamics in the early evolution of feathers. Jerry points out that you had to have feathers first, so the first appearance of feathers must have had some other advantage.

However, without wishing to be cynical, maybe this is all a big yawn. Certainly, it will be tough to get such papers published it high ranking journals again (I can’t see Nature filling its pages with pretty reconstructions of feathered dinos), so unless they can work out what colour Stegosaurs were (they didn’t have feathers. We think), or make some similar striking novel insight it I reckon that’s it.

Indeed, depending on how complicated it is to carry out these analyses (and only a few fossils apparently retain the necessary melanosomes) there may even be a decline in this kind of work, because it couldn’t be published in the likes of Nature or Science, in that it would just be one more coloured dinosaur.

However, there is another point, raised by two posters, Bex and Finch, on my previous article. Both of them yawned, for different reasons. Are they right?

Bex: Are you sure this is a very relevant issue? I mean, yes, it may be interesting … the possibility to provide some (feeble) inferences on behaviour, maybe even metabolism. But maybe this is not so amazing. Maybe it is just … cool: arresting images, nice colours, and the old stuff about charming dinosaurs. “Nature” seems to love appealing news, they are more attractive that … “tedious science”! Maybe dinosaurs had blue tails, maybe Neanderthals had red hair. Science or gossip? Once more, this is interesting, but … so much interesting?

Finch: Although interesting, I see nothing surprising in this article. It is just one of a number of “cosmetic” articles that journals like Nature love to publish. I mean there is not much science in this article, but many funny and cool things for newspapers and media, in general. Moreover, the title of this article, as well as many statements done throughout the text, are very misleading. In fact, the results of this study just show that some coelurosaurs had pigments in their (proto)feathers, while the authors use the term “dinosaurs”, which includes many many more species than coelurosaurs does. Of course, it is more cool to say that dinosaurs had colors, but this statement is not scientific and conveys the false message that dinosaurs like T. rex or Triceratops had colored feathers. Just imagine if Spielberg just read the title and decides to make a Jurassic Park 4 with a T. rex in red and blue feathers! Yes, very cool, but not real!

06/02/2010

DAWKINS ON HAMILTON

BBC Radio 4 has a series called “Great Lives”. The latest episode focused on the man who was probably the greatest evolutionary biologist in the second half of the 20th century, Bill Hamilton. His scientific papers are rather difficult to understand, being largely mathematical. But his ideas, in particular those leading to his theory of kin selection as an explanation of altruism, have been amazingly influential. Richard Dawkins, who popularised Hamilton’s ideas (without the maths) in The Selfish Gene, is on excellent form in this programme, together with Hamilton’s sister, Dr Mary Bliss. 30 minutes of excellent listening.

Click here to listen.

05/02/2010

NAME THAT ANIMAL!

Courtesy of Laura Riding (class of 06). What are they, and how many of them are there?