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Date of earliest animal life reset by 30 million years

June 28, 2012

The discovery was made by U of A geologists Ernesto Pecoits and Natalie Aubet in Uruguay. They found fossilized tracks a centimeter-long, slug-like animal left behind 585 million years ago in silty, shallow-water sediment.

A team of U of A researchers determined that the tracks were made by a primitive animal called a bilaterian, which is distinguished from other non-animal, simple life forms by its symmetry -- its top side is distinguishable from its bottom side -- and a unique set of "footprints."

U of A paleontologist Murray Gingras says fossilized tracks indicate that the soft-bodied animal's musculature enabled it to move through the sediment on the shallow ocean floor. "The pattern of movement indicates an evolutionary adaptation to search for food, which would have been organic material in the sediment," he said.

There were no fossilized remains of a bilaterian's body, just its tracks. "Generally when we find tracks of a soft-bodied animal, it means there's no trace of the body because they fossilize under different conditions," said Gingras. "It's usually just the body or just the tracks, not both."

It took more than two years for the U of A team members to satisfy themselves and a peer review panel of scientists that they had the right age for the bilaterian fossils.

U of A geochronologist Larry Heaman was among a group that returned to Uruguay to collect more fossil samples locked in a layer of sandstone. Heaman says because the depositional age of the sandstone is difficult to determine, they focused their investigation on particles of granitic rock found invading the sandstone samples.

Heaman explains that the granitic rocks were put through the university's mass spectrometry equipment, a process in which samples are bombarded by laser beams and the resulting atom- to molecule-sized particles are analyzed and dated.

Over the course of his U of A career, Heaman has taken part in a number of breakthrough research projects involving fossils. Last year he got the attention of the paleontology world when he confirmed the surprising date of a fossilized dinosaur bone found in New Mexico. Using U of A equipment, Heaman determined that the bone came from a sauropod, a plant-eating dinosaur that was alive some 700,000 years after the mass-extinction event that many believe wiped out all dinosaur life on Earth.

Heaman says the challenge in dating the bilaterian fossil makes it stand out from his other work. "This was the top research accomplishment because it has more direct relevance to the evolution of life as we know it," he said. "It was such a team effort; any one of us on our own couldn't have done this."

Before the U of A bilaterian find, the oldest sign of animal life was dated at 555 million years ago, from a find made in Russia.

Kurt Konhauser, a U of A geomicrobiologist, says the team's discovery will prompt new questions about the timing of animal evolution and the environmental conditions under which they evolved.

"This research was a huge interdisciplinary effort and shows the depth of the research capabilities here at the U of A," said Konhauser. "The challenge brought the sciences of geology, paleontology, geomicrobiology and geochronology together to nail down the age of the fossils."

Konhauser explains that in the past, research into the earliest signs of animal life would typically shift the date back by a few million years, but the U of A's finding of 30 million years is a real breakthrough.

The U of A's research team includes Ernesto Pecoits, Natalie Aubet, Kurt Konhauser, Larry Heaman, Richard Stern and Murray Gingras. The research was published June 28 in the journal Science.

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Story Source:

The above story is reprinted from materials provided by University of Alberta. The original article was written by Brian Murphy.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

  1. Ernesto Pecoits, Kurt O. Konhauser, Natalie R. Aubet, Larry M. Heaman, Gerardo Veroslavsky, Richard A. Stern, and Murray K. Gingras. Bilaterian Burrows and Grazing Behavior at >585 Million Years AgoScience, 29 June 2012 DOI:10.1126/science.1216295

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Submitted by: Unknown (via Beth Zimmerman)  Future evolution

This is beautiful!

My friend Estrella found that gif! it's very cool!

Hey, check out THE BEST poem about Darwin and The Origin of the Species EVER.

I posted it here


Carl Zimmer in The Loom:

Zimmer-NG-face-280When biologists think about the evolution of life, they think about climbing mountains.

To understand their alpine frame of mind, imagine a biologist studying the fish in a lake. Each fish may be born big or small. Fish born at certain sizes may be more likely to survive and reproduce than others. Each fish may be aggressive or shy. Again, their aggressiveness may determine their odds of having babies.

To picture all of this, it’s very helpful to imagine a landscape. Each point on that landscape is a different combination of aggression and body size. They’re like the longitude and latitude on a map. Each combination leads to a particular level of reproductive success. Picture that success as the elevation of that point on the landscape. The more success, the higher the altitude.

The biology of those fish can give the landscape a topography. Perhaps it produces a single mountain. The peak is the combination of weight and aggression that produces the most possible babies. The landscape drops off in all directions, to combinations that make it more likely the fish will die, or fail to reproduce.

The actual fish in the actual lake might turn out to be clustered on one of the mountain’s flanks. The fish closer to the peak have more babies than the others further downhill. As a result, they’ll pass down more copies of their genes to the next generation. And that means that the population will climb up towards the peak. If a new mutation arises, natural selection will favor it if it helps the fish climb further. Eventually, the fish may reach the mountaintop. Once they plant their flag on the peak, they’ll be stuck. Natural selection won’t be able to nudge them off.

Now imagine that there are two peaks, not one. The fish sit on one mountaintop, while the second peak towers over them in the distance. They can’t get to that second peak, though, because natural selection can only nudge them uphill. They are stuck with a mediocre body.

More here.

Posted by S. Abbas Raza at 11:41 PM | Permalink

What evidence looks like:

Sad news from Turkey:

Turkey suppresses evolution books

From LiveLeak and the Turkish Hurriyet Daily News, we learn that the Turkish government has suspended both the publication and sale of any book that promotes the theory of evolution. LiveLeak:

The Scientific and Technical Research Council of Turkey (TÜBİTAK) has put a stop to the publication and sale of all books in its archives that support the theory of evolution, daily Radikal has reported.

The evolutionist books, previously available through TÜBİTAK’s Popular Science Publications’ List, will no longer be provided by the council.

The books have long been listed as “out of stock” on TÜBİTAK’s website, but their further publication are now slated to be stopped permanently.

Books by Richard Dawkins, Alan Moorehead, Stephen Jay Gould, Richard Levontin and James Watson are all included in the list of books that will no longer be available to the Turkish readers.

The Scientific(?) and Technical Research Council of Turkey has been taken over by zealots? Now they claim it is not the case.

More on this:

The Scientific and Technical Research Council of Turkey (TÜBİTAK) has strongly denied reports that it has stopped printing books on evolution, saying the claims were “black propaganda” against their institution.

“If we aim to censor Evolution Theory we would discontinue publishing any books containing evolutionist approaches, but on the contrary we are publishing the books that are not being published by other publishing houses,” an official from TÜBİTAK told the Hürriyet Daily News yesterday in a phone interview.

A number of reports in daily Sözcü claimed Jan. 14 that TÜBİTAK had put a stop to the publication and sale of all books in its archives that support the theory of evolution.

The evolutionist books, previously available through TÜBİTAK’s Popular Science Publications’ List, will no longer be provided by the council, the daily had claimed.

Titles from prominent writers including Richard Dawkins, Alan Moorehead, Stephen Jay Gould, Richard Levontin and James Watson were listed as being among those which would no longer be available to Turkish readers.

However, the official refuted the claims. “There are two books already in our 2012 catalogue regarding evolution, Richard Dawkins’ ‘The Blind Watchmaker’ is one of them … Dawkins’ ‘The Selfish Gene’ is not being published because of a publication rights issue, but this is being manipulated,” the official said.

He claimed that “some circles” had kicked off a “black propaganda” campaign against TÜBİTAK to “shadow its success,” following the successful mission of Turkey’s first Earth observation satellite, Göktürk-2.

Göktürk-2 was launched Dec. 18 in China, but Prime Minister Recep Tayyip Erdoğanfollowed the launch at Ankara’s Middle East Technical University (ODTÜ) campus, which witnessed huge numbers of students protesting the prime minister’s visit. 

Erdoğan had called on the academics who supported the students to resign, but the police’s heavy-handed intervention in the protests also stirred a debate among Turkish universities, with some backing the police and Erdoğan and some opposing.

TÜBİTAK had previously been the target of evolutionist circles for alleged censorship practices. 

In early 2009 a huge uproar occurred when the cover story of a TÜBİTAK publication was pulled, reportedly because it focused on Darwin’s theory of evolution. The incident led to intense criticism and finger-pointing from various representatives of the publication and its parent institute. 

A few months later, the article in question appeared as the publication’s cover story.



Howard Falcon-Lang in BBC News:

_48935355_cloudforestotherTwo hundred years ago, Ascension Island was a barren volcanic edifice.

Today, its peaks are covered by lush tropical "cloud forest".

What happened in the interim is the amazing story of how the architect of evolution, Kew Gardens and the Royal Navy conspired to build a fully functioning, but totally artificial ecosystem.

By a bizarre twist, this great imperial experiment may hold the key to the future colonisation of Mars.

The tiny tropical island of Ascension is not easy to find. It is incredibly remote, located 1,600km (1,000 miles) from the coast of Africa and 2,250km (1,400 miles) from South America.

Its existence depends entirely on what geologists call the mid-Atlantic ridge. This is a chain of underwater volcanoes formed as the ocean is wrenched apart.

Ascension is one of a number of volcanic islands in the South Atlantic

However, because Ascension occupies a "hot spot" on the ridge, its volcano is especially active. A million years ago, molten magma explosively burst above the waves.

A new island was born.

More here.

Posted by S. Abbas Raza at 12:34 PM | Permalink

Milk, meat and blood: how diet drives natural selection in the Maasai

This post is a little different from the usual fare at this blog, as I am discussing a paper on which I’m a co-author. My collaborators and I just put up a paper in the open-access journal PLOS ONE. We analyzed genetic data from members of the Maasai tribe in Kenya and detected genes related to lactase persistence and cholesterol regulation that are under positive selection.

The Maasai and their Diet

Maasai tribe member drinking blood. Image credit: Rita Willaert

The Maasai are a pastoralist tribe living in Kenya and Northern Tanzania. Their traditional diet consists almost entirely of milk, meat, and blood. Two thirds of their calories come from fat, and they consume 600 – 2000 mg of cholesterol  a day. To put that number in perspective, the American Heart Association recommends consuming under 300 mg of cholesterol a day. In spite of a high fat, high cholesterol diet, the Maasai have low rates of diseases typically associated with such diets. They tend to have low blood pressure, their overall cholesterol levels are low, they have low incidences of cholesterol gallstones, as well as low rates of coronary artery diseases such as atherosclerosis.

Even more remarkable are the results of a 1971 study by Taylor and Ho. Two groups of Maasai were fed a controlled diet for 8 weeks. One group – the control group – was given food rich in calories. The other group had the same diet, but with an additional 2 grams of cholesterol per day. Both diets contained small amounts of a radioactive tracer (carbon 14). (You’d never get approval for a study like this today, and for good reason.) By monitoring blood and fecal samples, the scientists discovered that the two groups had basically identical levels of total cholesterol in their blood. In spite of consuming a large dose of cholesterol, these individuals had the same cholesterol levels as the control group.

Here is how the authors concluded their study:

This led us to believe, but without direct proof, that the Masai have some basically different genetic traits that result in their having superior biologic mechanisms for protection from hypercholesteremia

Motivated by these results, we set out to identify genes under selection in the Maasai as a result of these unusual dietary pressures. We scanned the genome looking for genetic signatures of natural selection at work.

The Data

Our data comes from the International HapMap Project, a collaborative experimental effort to study the genetic diversity in humans. The HapMap Project has collected DNA from groups of people from genetically diverse human populations with ancestry in Africa, Asia and Europe. Their anonymized data is publicly available for free. One of the HapMap populations is a group of Maasai from Kinyawa, Kenya  (n=156), and this is the population that we focus on.

DNA sequences on a part of Chromosome 7 from two random individuals, with the differences shown in red.

HapMap does not sequence full genomes, as this would have been prohibitively expensive at the time of data collection. Instead, they employ a shortcut. If you take my DNA sequence and line it up against yours, the two sequences will be about 99.9% similar. But every once in a thousand letters, or so, there will be a difference. You may have an A where I have a C. The HapMap group measures the DNA sequence at these very locations, where humans are known to vary from each other. In essence, they’re sampling the genome, looking only at sites where we expect to see variation. In the jargon of the field, this method is called looking for Single Nucleotide Polymorphisms, or SNPs (pronounced snips).

Hunting for signatures of selection in genetic data

Once you have the data, what can you do with it? We wanted to detect signs of natural selection. The basic idea behind detecting selection in genomic data is quite simple, and it has to do with sex. Every sperm or egg cell that you produce contains a single genome, which is formed by shuffling together the two sets of genomes that you inherited from your parents. Viewed this way, the role of sex is to shuffle together the genomes in a population into new combinations. If you compare the DNA sequences of a group of people, you will see signs of this shuffling.

The effect of sex is to shuffle genomes, in a process known as genetic recombination.

Now lets add natural selection to the mix. What happens if an individual is born with a new mutation that benefits their survival? Over time, you’d expect to see this mutation rise in frequency. Descendants of this individual will be over-represented in the population, as the fraction of people with this beneficial mutation goes up. In essence, the fingerprint of such selection is a reduction of genomic diversity. (I’m describing a particular model of selection here, known as positive natural selection. Some other types of selection can increase diversity, such as the selection on viruses to evade recognition by their host’s immune system.)

A new beneficial mutation arises in an individual (shown in red). It will rise in frequency in the population, leading to a characteristic reduction in diversity. Over time, genetic recombination and new mutations will build back the diversity, and the signal is lost.

Eventually, new mutations will creep in again, and generations of sexual reproduction would build back the diversity. However, if the loss of diversity was sudden enough (strong selection) and not too long ago, you can still detect it today. There are statistical tests (FstiHSXP-EHH) that can formally detect if the reduction in diversity at a given region is sufficient to infer selection. Sabeti et al have a nice review paper that discusses the different methods available to detect selection using genomic data.

Our Results

We used three different methods to detect selection, and our top candidate regions under selection are considered significant by at least two of the methods.

The strongest signal of selection, detected by all 3 methods, was a region on Chromosome 2 containing the Lactase gene (LCT), responsible for breaking down the lactose present in milk. Mutations in a neighboring gene in the cluster, MCM6, are associated with the ability to digest lactose in adulthood.

The strongest signal of selection was a region on Chromosome 2 that contained the LCT gene producing lactase, the enzyme that breaks down the lactose in milk. Interestingly, the default state in all adult mammals is to stop producing lactase in adulthood – our ancestors were all ‘lactose intolerant’. This makes sense from an evolutionary point of view, it forces children to wean from milk, and frees up the mothers resources. It turns out that different sets of mutations arose that gave European and African pastoralists the ability to digest milk. Those of us whose ancestors weren’t pastoralists still have trouble digesting milk.

This is a classic example of a selective sweep – a mutation confers an advantage (the ability to digest milk), and then sweeps through a population like wildfire. This result has been previously described in European populations, and also in African populations (including the Maasai) by Sarah Tishkoff and collaborators. Given that the Maasai consume large amounts of milk, it is not surprising that we see a very strong signal at this locus. We sequenced DNA in this region to confirm this result and, sure enough, we found that one of the lactase persistence conferring mutations identified by Tishkoff was present in the HapMap Maasai samples.

Two of the tests for selection that we used require that you make comparisons with another population. We chose the Luhya of Kenya as a our reference population. Among all the protein-altering mutations present in the data, the one that showed the largest population difference between the Maasai and Luhya (as measured by Fst) sits in the gene for a fatty acid binding protein FABP1. This protein is expressed in the liver, and the variant that occurs at higher frequency in the Maasai is associated with a lowering of cholesterol levels in Northern German women (n = 826) and in French Canadian men consuming a high fat diet (n = 623). Furthermore, studies in mice fed a high fat, high cholesterol diet showed that deactivating the FABP1 protein leads to protection against obesity, and lower levels of triglycerides in the liver, when compared to normal mice on an identical diet. These results suggest that this protein plays a role in regulating lipid homeostasis, and its selection in the Maasai may be diet-related.

On Chromosome 7, two of the methods we used to detect selection identified a cluster of genes that fall in the Cytochrome P450 Subfamily 3A (CYP3A). This family of genes is involved in drug metabolism, in oxidizing fatty acids, and in synthesizing steroids from cholesterol.

What’s next?

Computational methods can only take you so far. We have identified genes in candidate regions undergoing positive natural selection in the Maasai, possibly arising due to their unusual diet. But the case for selection can only be definitively made with an experimental study targeted to address the role of these genes in maintaining cholesterol homeostasis. We’re hoping to collaborate with experimental biologists to take these hypotheses forward and investigate their role in the evolutionary history of the Maasai.

So head over to PLOS, check out the paper, and let us know what you think.

Update: Here’s another blog post that discusses the paper, focusing more on the mixed genetic makeup of the Maasai.


Kshitij Wagh, Aatish Bhatia, Gabriela Alexe, Anupama Reddy, Vijay Ravikumar, Michael Seiler, Michael Boemo, Ming Yao, Lee Cronk, Asad Naqvi, Shridar Ganesan, Arnold J. Levine, Gyan Bhanot (2012). Lactase Persistence and Lipid Pathway Selection in the Maasai PLOS ONE, 7 (9) :10.1371/journal.pone.0044751

If you’d like to read more about selective sweeps, you may enjoy my post Why moths lost their spots, and cats don’t like milk. Tales of evol...


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