We keep hearing from Intelligent Design Creationists that the fossil record is lacking in transitional fossils. To support their claims, they consistently quote mine statement by Gould and others while ignoring the actual data.
Thanks to modern technology, Youtube presents Transitional Fossils I and II by DonExodus2
From Cassini Raw Images, specifically here.
I missed this one a week or two ago. Simon Conway Morris and his colleague Jean-Bernard Caron published a paper in Science on a new Cambrian fossil called Orthrozanclus. The cool thing about the fossil is that it combines features from two other fossils that Conway Morris previously implicated as transitional stem groups between the modern crown groups (“phyla”) of mollusks, annelids, and brachiopods: Wiwaxia and Halkeria. Of course, according to Discovery Institute propaganda, transitional fossils like this don’t exist.
Here is a news summary. See also the Orthrozanclus post from PZ Myers, his post last year on another stem group mollusk-ish critter, Odontogriphus.
Titan Has Liquid Lakes, Scientists Report in Nature Jan. 3, 2007 (Source: JPL)
Liquid Lakes on Titan The existence of oceans or lakes of liquid methane on Saturn’s moon Titan was predicted more than 20 years ago. But with a dense haze preventing a closer look it has not been possible to confirm their presence. Until the Cassini flyby of July 22, 2006, that is.
Scientists report definitive evidence of the presence of lakes filled with liquid methane on Saturn’s moon Titan in this week’s journal Nature cover story.
Radar imaging data from a July 22, 2006, flyby provide convincing evidence for large bodies of liquid on Titan today. A new false-color radar view gives a taste of what Cassini saw. Some highlights of the article follow below.
It is well known that The Panda’s Thumb is not just an evolution blog, it is also occasionally a Cassini-Huygens fanclub blog. We live-blogged the Huygens landing, and gushed over the discovery of stream channels (although annoyingly the methane oceans have not yet appeared, there clearly is some kind of methalogical cycle going on).
Someone has finally done the obvious thing and put together all of the Huygens images into a continuous animation. See the one with narration and the one with boops and beeps indicating various onboard processes. The fisheye camera perspective is kind of weird but we get a much better picture of what the surface topography looked like up close than we did from just the isolated snapshots.
It all just makes me wish they’d put a balloon and one of them plutonium-fueled Radioisotope Thermoelectric Generators on Huygens so that it could float around for a few months at 10 k elevation and give us some more details of what is down there.
While I’m demanding things from NASA, here are my other requests for the Cassini mission if it goes into “extra innings” like other recent NASA missions have: (1) get some more images of the Giant Equatorial Ridge on Iapetus, (2) full radar map of Titan’s surface, and then (3) a suicide mission to get a really super-up-close view of Saturn’s rings. I want to see the individual particles, darn it! A friend tells me there is no way to slow down the Cassini craft enough to get both slow enough and close enough to image 1-meter ice boulders, but I don’t buy it. There has got to be a way!
Seems like convergent evolution has been a hot topic recently. (See, for example, this recent PT post.)
On January 25th, the National Geographic reported that
After languishing for decades in the bowels of a New York museum, a dinosaur- era crocodile relative is seeing the light—and shedding secrets. New studies of the forgotten fossil reveal that the species walked on two feet and looked much like a so-called ostrich dinosaur, though the two are barely related, paleontologists report.
The specimen, Effigia okeeffeae, languished at the American Museum of Natural History for almost 60 years since its discovery at the Ghost Ranch quarry in New Mexico, near the digs of artist Georgia O’Keeffe, after whom the creature is named.
The recent efforts to map various genetic characteristics of humans are beginning to yield insights into what makes us Homo sapiens at the most basic levels. John Hawks draws attention to a paper published this week in PNAS. The paper uses statistical analysis of the distributions of linkage disequilibria in single-nucleotide polymorphisms (SNPs) to detect genes under recent selection pressure, and finds that at least 10% of human genes have been under such selection. (The percentage is an under-estimate because the coverage of SNPs is skewed to higher frequencies.) Many genes under recent selection cluster into four main groupings: “host-pathogen interactions, reproduction, protein metabolism, and neuronal function”. That last, of course, is real interesting! They offer some tentative explanations for the groupings:
We outline several predominant biological themes among genes detected with this strategy and suggest that selection for alleles in these categories accompanied the major “out of Africa” population expansion of humankind and/or the radical shift from hunter–gatherer to agricultural societies .
See Hawks’ blog entry for a more discussion and the paper itself, which is free online.
RBH
Resistance to antibiotics has been a concern of scientists almost since their widespread use began. In a 1945 interview with the New York Times, Alexander Fleming himself warned that the misuse of penicillin could lead to selection of resistant forms of bacteria, and indeed, he’d already derived such strains in the lab by varying doses of penicillin the bacteria were subjected to. A short 5 years later, several hospitals had reported that a majority of their Staph isolates were, as predicted, resistant to penicillin. This decline in effectiveness has led to a search for new sources and kinds of antimicrobial agents. One strategy involves going back to a decades-old approach researched by Soviet scientists: phage therapy. Here, they pit one microbe directly against another, using viruses called bacteriophage to infect, and kill, pathogenic bacteria. Vincent Fischetti at Rockefeller University has used this successfully to kill anthrax, Streptococcus pyogenes, and others. Another novel source of antibiotics has come from our own innate immune system, one of our initial defenses against microbial invaders.
The Washington Post today reminds us that there has been little progress in uncovering the source of the 2001 anthrax attacks.[1]
Why is this news for Panda’s thumb? Read on…
A male fly's sexual courtship of a female fly is a complicated business of tapping, singing, wing vibration, and licking, but a single gene is all that is needed to produce this complex behavior, according to new research published in this week's issue of the journal Cell.See also: Ebru Demir and Barry J. Dickson: "fruitless Splicing Specifies Male Courtship Behavior in Drosophila" Cell, Vol. 121, 785–794, June 3, 2005. DOI 10.1016/j.cell.2005.04.027The gene encodes the Fruitless protein. Male and female flies carry different versions of the fruitless protein, as a result of sex-specific splicing of the mRNA. The male form of Fruitless is critical for the male courtship ritual and males' preference for mating with females, as previous studies have shown.
Now, Barry J. Dickson and Ebru Demir of the Institute of Molecular Biotechnology of the Austrian Academy of Sciences show just how intimately fruitless is linked to these stereotypically male behaviors. They discovered that female flies with the male version of fruitless behave like males, directing at other females a sexual display nearly identical to their male counterparts.
All animals exhibit innate behaviors that are specified during their development. Drosophila melanogaster males (but not females) perform an elaborate and innate courtship ritual directed toward females (but not males). Male courtship requires products of the fruitless (fru) gene, which is spliced differently in males and females. We have generated alleles of fru that are constitutively spliced in either the male or the female mode. We show that male splicing is essential for male courtship behavior and sexual orientation. More importantly, male splicing is also sufficient to generate male behavior in otherwise normal females. These females direct their courtship toward other females (or males engineered to produce female pheromones). The splicing of a single neuronal gene thus specifies essentially all aspects of a complex innate behavior.Petra Stockinger, Duda Kvitsiani, Shay Rotkopf, László Tirián, and Barry J. Dickson: "Neural Circuitry that Governs Drosophila Male Courtship Behavior" Cell, Vol. 121, 795–807, June 3, 2005. DOI 10.1016/j.cell.2005.04.026
Male-specific fruitless (fru) products (FruM) are both necessary and sufficient to “hardwire” the potential for male courtship behavior into the Drosophila nervous system. FruM is expressed in ∼2% of neurons in the male nervous system, but not in the female. We have targeted the insertion of GAL4 into the fru locus, allowing us to visualize and manipulate the FruM-expressing neurons in the male as well as their counterparts in the female. We present evidence that these neurons are directly and specifically involved in male courtship behavior and that at least some of them are interconnected in a circuit. This circuit includes olfactory neurons required for the behavioral response to sex pheromones. Anatomical differences in this circuit that might account for the dramatic differences in male and female sexual behavior are not apparent.
Frodo Baggins [L], Aragorn [R]?
Several of the fossils of the celebrated “hobbit-sized” hominid Homo floresiensis have apparently been irreparably damaged by the researcher who spirited them away from the discovery team for months. This strange and sad story first appeared in USA Today on March 21st, and was reported in Science on 25 March 2005; (307: 1848)
Usually Carl Zimmer’s The Loom keeps us up to date on the diminutive Homo floresiensis with great posts like this one, but he must be really busy this week.
Anyway, here follows the sad news from USA Today.
I’d like to point you to a new website, EvolNews.org!:
Welcome to EvolNews.org!
EvolNews.org is a site geared toward sharing new and interesting research in Evolutionary Biology with other researchers and with anyone interested. Face it, you’re a busy researcher- and you probably find all fields of Evolutionary Biology interesting, but you barely have time to keep current with the research in your own sub-discipline. Well, this web site is designed to give a brief summary of the latest breaking news in evolutionary research that occurs in peer-reviewed journals, and provide you with handy-dandy links to the articles. There is also the ability to start discussions by posting replies to the articles, but that is for the readership to decide. We are always open to suggestions to improve the website, including adding new topic areas and features, as it’s all fairly uncomplicated with the wonderful software PHP-Nuke. What this site will not support is teologlogical debates, creationism/evolution debates, etc.- although they can be presented as articles and comments if published elsewhere.
I daresay that it is a good thing that they avoid “teologlogical debates,” given the mess they made of the word “teleological”. Never fear, that is what Panda’s Thumb is for!
New Scientist reports on the findings of a study on the impact of genes on religious inclinations
Genes may help determine how religious a person is, suggests a new study of US twins. And the effects of a religious upbringing may fade with time.
Until about 25 years ago, scientists assumed that religious behaviour was simply the product of a person’s socialisation - or “nurture”. But more recent studies, including those on adult twins who were raised apart, suggest genes contribute about 40% of the variability in a person’s religiousness.
But it is not clear how that contribution changes with age. A few studies on children and teenagers - with biological or adoptive parents - show the children tend to mirror the religious beliefs and behaviours of the parents with whom they live. That suggests genes play a small role in religiousness at that age.
Now, researchers led by Laura Koenig, a psychology graduate student at the University of Minnesota in Minneapolis, US, have tried to tease apart how the effects of nature and nurture vary with time. Their study suggests that as adolescents grow into adults, genetic factors become more important in determining how religious a person is, while environmental factors wane.
The study can be found in Journal of Personality (vol 73, p 471)
Well, it’s better than boiling mud (1). One of the iconic images of Australia is the Merino sheep, an extremely woolly, arid-land adapted animal that is the backbone of our wool industry. One draw back of their wooliness is that urine and feces accumulate on the sheep’s wool between the hind legs. This attracts flies that lay eggs there, and when the maggots hatch they start eating the sheep alive.
To combat this “fly strike”, Australian farmers have surigally removed the wool-bearing skin between the sheep’s hind legs, a process called Mulesing. This is done without anaesthesia on farms, so the Animal rights group PETA has kicked up a fuss and there is a looming trade boycott on Australian wool.
However, just recently a group of mutant sheep were found on a remote property here in South Australia (listen to the audio presentation for full details). The sheep lack the wool and the folds of skin between the legs found on normal Merinos, and so are relatively immune to fly strike. It remains to be seen if this beneficial mutation can be bred into Australia’s herd successfully, but it would be amusing if the wrath of PETA was averted by mutant sheep.
(1) The title is taken from comedian John Clarke’s alternative national anthem “God Loves New Zealand, He gave us Boiling Mud”
Here’s a provocative exclusive from Space.com:
Exclusive: NASA Researchers Claim Evidence of Present Life on Mars.
A pair of NASA scientists told a group of space officials at a private meeting here Sunday that they have found strong evidence that life may exist today on Mars, hidden away in caves and sustained by pockets of water.
The scientists, Carol Stoker and Larry Lemke of NASA’s Ames Research Center in Silicon Valley, told the group that they have submitted their findings to the journal Nature for publication in May, and their paper currently is being peer reviewed.
What Stoker and Lemke have found, according to several attendees of the private meeting, is not direct proof of life on Mars, but methane signatures and other signs of possible biological activity remarkably similar to those recently discovered in caves here on Earth.
If confirmed, this could have some serious ramifications for evolution on the early Earth. Did living things go from Mars to Earth or vice versa? Are we talking about multiple origin of life events? Interesting stuff. I guess we’ll have to live with a mere teaser for now.
For Darwin Day (Feb 12th), the Canberra Skeptics arranged a talk by paleoanthropologist Colin Groves at the National Museum of Australia on the subject of Homo floresiensis, the “Hobbit”. It’s clearly a popular subject; the small lecture theatre was filled to capacity with a few hundred people.
Some scientists have disputed the idea that floresiensis is a new species, suggesting instead that the skeleton is a pathological modern human - Maciej Henneberg, for one, has claimed that it closely resembles a 4000-year-old microcephalic skull found on Crete. Groves showed pictures of that skull and compared it to the hobbit. They did not look very similar to my unqualified judgement, nor, apparently, to the judgement of many qualified scientists. The hobbit femur also has differences from that of any other hominid, and the pelvis flares more than in H. sapiens or H. erectus.
From the [u]Biology is Cool[/u] division at the Thumb. According to [Enable javascript to see this email address.]:
Canopy-dwelling ants in the tropical forests of the Americas have adopted a neat way of averting disaster should they fall from their perch. They glide to safety, steering towards their home trunk rather than plummeting to the ground, where they might never see their nest-mates again.[Enable javascript to see this email address.]
If you don’t believe it, read the news article, the far-too uncreatively-named Nature paper “Directed aerial descent in canopy ants“, or better yet, watch the video.
How was this fascinating discovery made?
The discovery was an accident, [Stephen] Yanoviak recalls. “About two years ago I was climbing trees to collect mosquitoes when I was attacked by these ants. I brushed 20 or 30 of them off; they fell down and made a nice J-shaped curve back to the tree.”[Enable javascript to see this email address.]
Thus a Nature paper was born…
Since you asked, Stephen P. Yanoviak is indeed a Project Steve Steve.
Creationists often dismiss examples of evolutionary change as “that’s just a loss of information.” There are many problems with this claim (see also here and here), but here is a new one: it appears that in at least one case, humans evolved by “loss of information” (in this case, loss of a gene) from their apelike ancestors. Carl Zimmer mentions this in passing in a post on the cell-surface sugars, Neu5Ac and Neu5Gc:
The European Space Agency has put up a mosaic of the images taken during the Huygens descent.
I think that Huygens landed in the middle of the dark stuff. If so, the images and data from the surface indicate that this isn’t strictly an “ocean,” rather it is some kind of spongy material. A giant hydrocarbon bog, perhaps? Huygens had a GC/MS on board that took samples for 70 minutes, so we should get a quite thorough analysis of the molecular composition of the atmosphere during descent, and the surface material.
The clouds/fog are also very interesting, if they represent “moisture” evaporating off of the “ocean” and then “raining” on the “land” to form the channels. We may be seeing a complete “hydrologic” cycle, except for the “hydro” part , since the molecules involved are hydrocarbons rather than H2O. It appears that a whole new vocabulary will be needed to describe the physical geography of Titan.
See also this article in The Scientist for what astrobiologists are saying:
Wow.
Huygens success = image = drainage pattern = rivers = rain = oceans.
(From CNN.)
Sometimes a picture really is worth a thousand words and a few billion dollars.
Since I need a few more lines to provide space for the image:
Wow.
Wowsers.
(etc.)
In what is turning out to be a pretty darn good week for science, the Huygens probe from the Cassini spacecraft has apparently entered the atmosphere of the shrouded moon Titan, the parachutes deployed, and data was successfully transmitted. This blows away all previous surface landings on extraterrestrial bodies and is, well, really cool.
Huygens-Cassini Live Blogging: Titan Touchdown
category - Science Update: 10:25 Cassini is now sending ‘dummy packets’. The signal has been acquired by JPL/ESA. Good news.
Update: 9:35 JPL Mission briefing. “We know all three parachutes did deploy and the heat shield worked. We know it survived for at least half an hour on the surface of Titan.” Note-some of the data intended for and likely received by Cassini “leaked” all the way to earth, in addition to the carrier signal, indicating data was received from onboard instruments. Cassini should turn to earth and start sending at 10:07 EST. 67 minutes later we begin to download Huygens data. It will take some time to compile
Update: 8:30 ESA/ESOC Mission briefing. Huygens is STILL transmitting earth time. Data Stream appears ‘very rich’. Huygens appears to have survived and is still transmitting well beyond impact/touchdown on Titan’s surface. Cassini will listen for Huygens’s signal as long as there is the slightest possibility that it can be detected. Once Huygens’s landing site disappears below the horizon, there’s no more chance of signal, and Huygens’s work is finished. Cassini-Huygens Data stream is scheduled to commence at 10:07 EST but will not be acquired until 11:14 EST earth time
Update: 7:50 Contact at JPL tells me that Earth bound radio observatory believes they also detected ‘solid’ image data from the DISR . This remains unconfirmed officially.
Update: 7:46 Data in stream confirmed. Doppler data from one of the onboard instruments was detected via earth bound observatory being transmitted to cassini. Hod damn I think this may have worked folks.
Update: 7:30 AM EST Mission Briefing From ESA/ESOC in Germany, reporting “We have a signal, so we know Huygens is alive”. “Signal was solid for a long time”. “Signal was solid for two hours!”. Confirmed data transmission from Huygens to Cassini by earth bound radio observatories world wide!! Very encouraging!!!!
BBC: Moon mission ‘probably a success’
Cassini webpage: Radio Astronomers Confirm Huygens Entry in the Atmosphere of Titan
Remember Cassini, the multibillion dollar spaceship we put in orbit around Saturn back in July? (If not, see the PT posts Say hello to Phoebe and First decent views of the surface of Titan, and the Cassini website).
Well, it has taken awhile for Cassini to do its first full orbit, but it is back in the inner Saturnian system, and today it completed its first flyby of Titan, the solar system’s largest moon and only moon with a thick atmosphere made of nitrogen and organic compounds.
Cassini will pass within 746 miles of Titan – a mere 10 hour drive on the freeway – and snap up close photos, and image the surface in detail with atmosphere-penetrating radar.
There’s a new article out about a new breakthrough in controlling pesticide resistant insects in Australia, one which involes trying to shut down their ability to resist pesticides:
Australian and British scientists have achieved a technical breakthrough to help control insects that have developed resistance to common agricultural pesticides, the New South Wales state government said on Thursday.
[…]
“Developed by the NSW Department of Primary Industries and Rothamsted Research in the UK, the technique relies on the use of naturally occurring enzyme inhibitors to disarm an insect’s defense system,” Macdonald said.
“The enzyme inhibitor acts first to shut down an insect’s resistance mechanisms. A few hours later, while the bug’s defenses are still low, the pesticide kicks in.”
A late notice:
After the successful series on ‘Evolution‘, PBS has started airing another excellent miniseries, this time on Origins. (Origins will appear on PBS on Sept. 28-29 at 8:00 p.m. EDT. (Check local listings).)
See Nova Origins website
This series documents in detail the historical trail allowing science to understand the historical links between the Big Bang all the way to our existence.
The website provides a wealth of resources, additional links and interviews.
From EurekAlert:
The morphological complexity of mammals, as compared to invertebrates, is thought to have arisen through advantageous genetic changes that occurred during the course of evolution. A new research study published in the September issue of Developmental Cell suggests that the evolution of higher-order vertebrate organ systems can result from primitive developmental genetic programs that are, in a sense, recycled for entirely new structures.
According to the expression patterns in the fruit fly, Drosophila, the ancestral action of the Hmx gene was limited to the development of the central nervous system (CNS). Dr. Thomas Lufkin from the Genome Institute of Singapore and colleagues show that the mouse Hmx2 and Hmx3 genes have apparently interchangeable functions in CNS development and have overlapping yet distinct functions in the development of the vestibular system of the inner ear, an organ that has no counterpart in Drosophila. The researchers found that when mice are genetically engineered to lack Hmx2 and Hmx3, Drosophila Hmx can substitute for the mouse Hmx3 gene in CNS development and, surprisingly, can also direct development of the inner ear. Therefore, a Drosophila gene can direct formation of an organ system that does not even exist in the Drosophila body.
“These results demonstrate that the evolution of higher vertebrate characteristics can result from the recycling or redeployment of ‘old’ genes in new parts of the embryo, rather than through mutation of gene protein-coding sequence alone. Old genes can be given a new purpose through ‘reassignment’ to organs undergoing evolutionary advancement. The reassignment likely comes through a shuffling of existing regulatory elements to generate new combinations that are specific to the new organ,” explains Dr. Lufkin.
###
Weidong Wang, J. Fredrik Grimmer, Thomas R. Van De Water, and Thomas Lufkin: “Hmx2 and Hmx3 Homeobox Genes Direct Development of the Murine Inner Ear and Hypothalamus and Can Be Functionally Replaced by Drosophila Hmx”
Developmental Cell, Volume 7, Number 3, September 2004, pages 439-453.
From EurekAlert:
One of the most debated hypotheses in evolutionary biology received new support today, thanks to a study by a scientist at the University of Nevada, Reno. Elissa Cameron, a mammal ecologist in the Department of Natural Resources and Environmental Science, has helped to disprove critics of a scientific theory developed in 1973.
At that time, ecologist Bob Trivers and mathematician Dan Willard said that large healthy mammals produce more male offspring when living in good conditions, such as areas where there is an ample food supply. Conversely, female mammals living in less desirable conditions would tend to have female offspring. …
She conducted an analysis of 1,000 studies that examined the Trivers-Willard hypothesis and sex ratios in mammals. Her study found that female mammals that were in better body condition during the early stages of conception were more likely have male offspring. Body fat and diet can affect levels of glucose circulating in a mammal’s body, and Cameron suggests that the levels of glucose around the time of conception could be influencing the sex of the animal’s offspring.
“A high-fat diet can result in higher levels of glucose, thereby supporting the hypothesis that glucose may be contributing to the sex of the mammal’s offspring,” Cameron said.
The paper is Elissa Z. Cameron, “Facultative adjustment of mammalian sex ratios in support of the Trivers-Willard hypothesis: evidence for a mechanism” Proceedings of the Royal Society of London, Ser. B. 271, 1723 - 1728 ( DOI: 10.1098/rspb.2004.2773).
Abstract:
Evolutionary theory predicts that mothers of different condition should adjust the birth sex ratio of their offspring in relation to future reproductive benefits. Published studies addressing variation in mammalian sex ratios have produced surprisingly contradictory results. Explaining the source of such variation has been a challenge for sex-ratio theory, not least because no mechanism for sex-ratio adjustment is known. I conducted a meta-analysis of previous mammalian sex-ratio studies to determine if there are any overall patterns in sex-ratio variation. The contradictory nature of previous results was confirmed. However, studies that investigated indices of condition around conception show almost unanimous support for the prediction that mothers in good condition bias their litters towards sons. Recent research on the role of glucose in reproductive functioning have shown that excess glucose favours the development of male blastocysts, providing a potential mechanism for sex-ratio variation in relation to maternal condition around conception. Furthermore, many of the conflicting results from studies on sex-ratio adjustment would be explained if glucose levels in utero during early cell division contributed to the determination of offspring sex ratios.
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The description of our site in the right sidebar says that “The Panda’s Thumb is the virtual pub of the University of Ediacara,” and the University of Ediacara (U of E) is “an online virtual University dedicated to the study of the origins of life in the cosmos.”
At the U of E site, Chris Nedin explains where the name “Ediacara” came from
The name “Ediacara” (pronounced Edi-ak-ra) comes from the Ediacara fauna, the first example of multicelled metazoans found in the fossil record. The significance of the fauna was first realized by geologists in South Australia, who found abundant fossils at the Ediacara Hills in the Flinders Ranges, about 650 km north of Adelaide. They realized that not only did the fauna contain jellyfish, soft corals and possibly worms and proto-arthropods, similar to modern forms, but that the fauna was significantly older than any other animal fossils yet found (600-540 million years old), even predating the Cambrian explosion. Whilst debate still continues as to the exact nature of the fauna, few now doubt that at least some of the forms represent examples of modern animal groups. The origin of the metazoa and thus all animal groups must now be placed even further back in time, and may never be found, since it is thought that the precursor organisms were miofaunal - tiny worm-like organisms living in the interstitial spaces between sand grains and thus having little chance of fossilizing.
“Ediacara” thus represents not only a major milestone in the history life on Earth, but also in the history of the Internet, being - as it is - the worlds first virtual university.
Apropos of this explanation, here’s a really neat story from the internet today. See here for the whole story and some neat pictures.
From ScienceDaily:
Comparing primate genomes is an approach that can help scientists understand the genetic basis of the physical and biochemical traits that distinguish primate species. James Sikela and colleagues, for example, collected DNA from humans, chimpanzees, bonobos, gorillas, and orangutans to identify variations in the number of copies of individual genes among the different species. Their work is published in this month’s issue of the open-access journal, PLoS Biology.
Overall, Sikela and colleagues found more than 1,000 genes with changes in copy number in specific primate lineages. All the great ape species showed more increases than decreases in gene copy numbers, but humans showed the highest number of genes with increased copy numbers, at 134, and many of these duplicated human genes are implicated in brain structure and function.
Because some of these gene changes were unique to each of the species examined, they will likely account for some of the physiological and morphological characteristics that are unique to each species. One cluster of genes that amplified only in humans was mapped to a genomic area that appears prone to instability in human, chimp, bonobo, and gorilla. This region has undergone modifications in each of the other descendent primate species, suggesting an evolutionary role. In humans, gene mutations in this region are also associated with the inherited disorder spinal muscular atrophy. This fact, along with the observation that there are human-specific gene duplications in this region, suggests a link between genome instability, disease processes, and evolutionary adaptation.
The research paper is available at the Public Library of Science - abstract is below:
Given that gene duplication is a major driving force of evolutionary change and the key mechanism underlying the emergence of new genes and biological processes, this study sought to use a novel genome-wide approach to identify genes that have undergone lineage-specific duplications or contractions among several hominoid lineages. Interspecies cDNA array-based comparative genomic hybridization was used to individually compare copy number variation for 39,711 cDNAs, representing 29,619 human genes, across five hominoid species, including human. We identified 1,005 genes, either as isolated genes or in clusters positionally biased toward rearrangement-prone genomic regions, that produced relative hybridization signals unique to one or more of the hominoid lineages. Measured as a function of the evolutionary age of each lineage, genes showing copy number expansions were most pronounced in human (134) and include a number of genes thought to be involved in the structure and function of the brain. This work represents, to our knowledge, the first genome-wide gene-based survey of gene duplication across hominoid species. The genes identified here likely represent a significant majority of the major gene copy number changes that have occurred over the past 15 million years of human and great ape evolution and are likely to underlie some of the key phenotypic characteristics that distinguish these species.
