Tuesday, May 5, 2009
Saturday, May 2, 2009
Origin confusion?
Science Magazine and the New York Times both reported this week on a new Africa-wide survey of human genetics, the largest ever to be conducted in that continent, which claims to pinpoint more closely the geographic origin of modern humans.
Unfortunately, the two articles appear to report conflicting results.
The New York Times’s Nicholas Wade reports, “The origin of species is generally taken to be the place where its individuals show the greatest genetic diversity. For humans, when the new African data is combined with DNA information from the rest of the world, this spot lies on the coast of southwest Africa near the Kalahari desert.”
Science Magazine’s “news” section, in contrast, says the study concludes that “East Africa was the source of the great migration that populated the rest of the world.”
I wasn’t able to access the researchers’ data or original report (it may not be online yet), which probably clears up this apparent contradiction. I’m assuming that Science’s “great migration” and the Times’s “origin of species” are actually two different things.
Nontheless—confusing! Those are the kinds of quotes that news sources can run with, and which might spread misinformation. I’ll post an update/clarification whenever I can get access to the actual research (…or when something comes up on the New York Times’s “corrections” page?). Responses welcome if anyone can figure out where the confusion lies.
The study’s data provides a lot more interesting information besides that on the “origin" question. Africa, despite being the continent with the greatest genetic diversity, has been underrepresented in genetic surveys, especially because the most diverse groups (like bushmen and hunter-gatherers) are logistically difficult to reach.
This group of researchers spent over 10 years collecting samples from some of the most remote populations in Africa, eventually ending up with blood from 3194 Africans in 113 different populations. They then searched the samples for over 1000 genetic markers, and sorted the DNA into similar clusters.
They found (luckily for them!) that those DNA-based clusters mapped well onto cultural and language groups. For example, the click-language groups—such as the Khoisan of south Africa and the Sandawe and Hazda of Tanzania—share common ancestors.
Researchers also found, through comparison with African-American DNA samples, that most African-Americans have ancestors from all over Africa, making it difficult to pinpoint a person’s origins to a specific group (as some DNA testing claims it can do).
There is hope the data will be used eventually for medical research--for example, to better understand why people respond differently to diseases and drugs.
Anne
Unfortunately, the two articles appear to report conflicting results.
The New York Times’s Nicholas Wade reports, “The origin of species is generally taken to be the place where its individuals show the greatest genetic diversity. For humans, when the new African data is combined with DNA information from the rest of the world, this spot lies on the coast of southwest Africa near the Kalahari desert.”
Science Magazine’s “news” section, in contrast, says the study concludes that “East Africa was the source of the great migration that populated the rest of the world.”
I wasn’t able to access the researchers’ data or original report (it may not be online yet), which probably clears up this apparent contradiction. I’m assuming that Science’s “great migration” and the Times’s “origin of species” are actually two different things.
Nontheless—confusing! Those are the kinds of quotes that news sources can run with, and which might spread misinformation. I’ll post an update/clarification whenever I can get access to the actual research (…or when something comes up on the New York Times’s “corrections” page?). Responses welcome if anyone can figure out where the confusion lies.
The study’s data provides a lot more interesting information besides that on the “origin" question. Africa, despite being the continent with the greatest genetic diversity, has been underrepresented in genetic surveys, especially because the most diverse groups (like bushmen and hunter-gatherers) are logistically difficult to reach.
This group of researchers spent over 10 years collecting samples from some of the most remote populations in Africa, eventually ending up with blood from 3194 Africans in 113 different populations. They then searched the samples for over 1000 genetic markers, and sorted the DNA into similar clusters.
They found (luckily for them!) that those DNA-based clusters mapped well onto cultural and language groups. For example, the click-language groups—such as the Khoisan of south Africa and the Sandawe and Hazda of Tanzania—share common ancestors.
Researchers also found, through comparison with African-American DNA samples, that most African-Americans have ancestors from all over Africa, making it difficult to pinpoint a person’s origins to a specific group (as some DNA testing claims it can do).
There is hope the data will be used eventually for medical research--for example, to better understand why people respond differently to diseases and drugs.
Anne
Crazy sea-grapes complicate Cambrian explosion
A submarine expedition to the Bahamas has discovered a new species—the “Bahamian groma”—a single-celled organism about one inch in diameter.
The creatures are reminiscent of grapes, or balloons, or “doo-doo balls,” according to researcher Sonke Johnson of Duke University.
Although similar mega-amoebas have been discovered around the world—the first in 2000 in the Arabian Sea—these are different in one important way: they’ve made tracks across the ocean floor. Although the grapes appear to be moving too slowly to be captured with the submarine’s video capabilities, researchers are convinced the tracks they’ve made can’t be created simply by ocean currents. The organisms sometimes head out in multiple directions from one spot, and are able to go up and down the ridges and valleys of the ocean floor.
The idea that such simple organisms could have created the tracks throws a wrench in current ideas about the Cambrian explosion—the rapid expansion of multicellular, complex life that happened about 530 million years ago.
Before discovering the creatures, themselves, researchers found grape-tracks in the pre-Cambrian fossil record and assumed this meant that bilateral creatures—the types of things we normally consider capable of making tracks—were around in pre-Cambrian days.
If, instead, the Bahamian groma were responsible for the tracks, it means that the Cambrian explosion may have been even more explosive than we thought, taking animal life from amoeba to us in a shorter amount of time than previously believed.
As far as researchers know, the Bahamian groma is like a giant balloon. Filled with water and almost neutrally buoyant, it floats along the very surface of the ocean floor by “eating” the stuff in front of it and “pooping” it out behind. They’re fragile and impossible to study in captivity, however, so nobody really knows.
They clearly reproduce, “because there were sure a lot of them,” says Johnson. But that process, as well, remains a mystery.
I learned about the grapes (and stole pictures) from this blog article, which referred me to this press release as well as the original 2008 paper in Current Biology, “Giant Sea-Protist Produces Bilaterian-like Traces.”
Interestingly, wikipedia’s Cambrian explosion entry mentions that Charles Darwin saw the Cambrian explosion “as one of the main objections that could be made against his theory of evolution by natural selection,” presumably because rapid diversification during the Cambrian period contradicted his ideas about slow, successive change. He acknowledges this in "Origin," saying that “several of the main divisions of the animal kingdom suddenly appear in the lowest known fossiliferous rocks,” and that this problem “at present must remain inexplicable, and may be truly urged as a valid argument against the views here entertained.”
-Anne
The creatures are reminiscent of grapes, or balloons, or “doo-doo balls,” according to researcher Sonke Johnson of Duke University.
Although similar mega-amoebas have been discovered around the world—the first in 2000 in the Arabian Sea—these are different in one important way: they’ve made tracks across the ocean floor. Although the grapes appear to be moving too slowly to be captured with the submarine’s video capabilities, researchers are convinced the tracks they’ve made can’t be created simply by ocean currents. The organisms sometimes head out in multiple directions from one spot, and are able to go up and down the ridges and valleys of the ocean floor.
The idea that such simple organisms could have created the tracks throws a wrench in current ideas about the Cambrian explosion—the rapid expansion of multicellular, complex life that happened about 530 million years ago.
Before discovering the creatures, themselves, researchers found grape-tracks in the pre-Cambrian fossil record and assumed this meant that bilateral creatures—the types of things we normally consider capable of making tracks—were around in pre-Cambrian days.
If, instead, the Bahamian groma were responsible for the tracks, it means that the Cambrian explosion may have been even more explosive than we thought, taking animal life from amoeba to us in a shorter amount of time than previously believed.
As far as researchers know, the Bahamian groma is like a giant balloon. Filled with water and almost neutrally buoyant, it floats along the very surface of the ocean floor by “eating” the stuff in front of it and “pooping” it out behind. They’re fragile and impossible to study in captivity, however, so nobody really knows.
They clearly reproduce, “because there were sure a lot of them,” says Johnson. But that process, as well, remains a mystery.
I learned about the grapes (and stole pictures) from this blog article, which referred me to this press release as well as the original 2008 paper in Current Biology, “Giant Sea-Protist Produces Bilaterian-like Traces.”
Interestingly, wikipedia’s Cambrian explosion entry mentions that Charles Darwin saw the Cambrian explosion “as one of the main objections that could be made against his theory of evolution by natural selection,” presumably because rapid diversification during the Cambrian period contradicted his ideas about slow, successive change. He acknowledges this in "Origin," saying that “several of the main divisions of the animal kingdom suddenly appear in the lowest known fossiliferous rocks,” and that this problem “at present must remain inexplicable, and may be truly urged as a valid argument against the views here entertained.”
-Anne
The origin of Native Americans
An interesting article came out a few days ago that settled the long-standing debate on whether Native Americans descended from one ancestral population or multiple populations.
Full text can be found here: http://www.sciencedaily.com/releases/2009/04/090428223836.htm
The article details a DNA study that provides very strong evidence for the descending of Native American populations from a single ancestral population. Says Karl Britt Schroeder, a lecturer at UC-Davis and one of the authors of the study:
"Our work provides strong evidence that, in general, Native Americans are more closely related to each other than to any other existing Asian populations, except those that live at the very edge of the Bering Strait"
The results of the study expands upon previous findings of what is termed the "9-repeat allele," which is a genetic marker that occurs in all 41 Native American populations sampled and is absent in all of the Eurasian, African, and Oceanian groups sampled. While the discovery of this allele strongly suggested the 'single ancestral population' theory, there was still a possibility that this allele's prominence could be due to mutations occuring separately in Native American populations or crossing over.
The study found that, in examining the bordering base pairs of the "9-repeat allele," there was a distinct pattern of base pairs not found in individuals without the allele, a pattern that is too short to have been promoted by positive selection and too prevalent to suggest multiple mutations. This is the first study supporting the 'single ancestral population theory' with evidence from DNA carried by both sexes.
In light of the results, it seems that the ancestors of the Native American population were indeed most likely to have been a single population that migrated in one wave to the Americas. This would account for the substantial genetic homogeneity both observed and inferred in Native American populations present and past, bringing to mind the innumerable cases discussed throughout the centuries of Native American populations genetically unequipped to combat foreign illnesses like smallpox.
-Andrew Plan
Full text can be found here: http://www.sciencedaily.com/releases/2009/04/090428223836.htm
The article details a DNA study that provides very strong evidence for the descending of Native American populations from a single ancestral population. Says Karl Britt Schroeder, a lecturer at UC-Davis and one of the authors of the study:
"Our work provides strong evidence that, in general, Native Americans are more closely related to each other than to any other existing Asian populations, except those that live at the very edge of the Bering Strait"
The results of the study expands upon previous findings of what is termed the "9-repeat allele," which is a genetic marker that occurs in all 41 Native American populations sampled and is absent in all of the Eurasian, African, and Oceanian groups sampled. While the discovery of this allele strongly suggested the 'single ancestral population' theory, there was still a possibility that this allele's prominence could be due to mutations occuring separately in Native American populations or crossing over.
The study found that, in examining the bordering base pairs of the "9-repeat allele," there was a distinct pattern of base pairs not found in individuals without the allele, a pattern that is too short to have been promoted by positive selection and too prevalent to suggest multiple mutations. This is the first study supporting the 'single ancestral population theory' with evidence from DNA carried by both sexes.
In light of the results, it seems that the ancestors of the Native American population were indeed most likely to have been a single population that migrated in one wave to the Americas. This would account for the substantial genetic homogeneity both observed and inferred in Native American populations present and past, bringing to mind the innumerable cases discussed throughout the centuries of Native American populations genetically unequipped to combat foreign illnesses like smallpox.
-Andrew Plan
Friday, May 1, 2009
Origin of life may not have been from hot soup
Darwin wrote that some "warm little pond" that contained all the necessary ingredients of life such as ammonia, light, heat, electricity, etc. would beget the first living creatures. This is not far from our current understanding of the primordial soup based on experiments by Urey and Miller that life had a "hot start". However, this belief has been under fire for some time because hot temperatures cannot support a stable environment for structures appropriate for life to form. However, new theories have emerged that so-called "psychrophiles", or cold-loving microbes, might be the new instigators of life. If we can imagine thermophiles living in hot sulfur springs, it's not too much of a stretch to imagine bacteria living in polar ice sheets and temperate glaciers. The sun's luminosity was 30% lower than now, producing a subzero earth.
Research in the past 10 years shows that freezing can concentrate and stabilize molecules more and allow formation of more complex structures. Experiments have shown that simple molecules trapped in ice veins can produce simple nucleic acids in the course of 30 years. However, I'm curious to know whether 30 years is an appropriate time frame for structure formation comparable to that in a hot environment. 30 years seems quite a contrast to the hot trigger from Urey and Miller's applied electricity. If a cold start is still questioned, the cold could've still acted as a selection factor for the common ancestral organism that gave rise to all life forms. Could that be defined as the more significant origin of life then? Well, the cold hypothesis can be quite powerful if seen in light of current exploration of possibilities of life on other worlds, i.e. Mars and various moons of Saturn. These are all very cold places!
-Bonnie Chien
Research in the past 10 years shows that freezing can concentrate and stabilize molecules more and allow formation of more complex structures. Experiments have shown that simple molecules trapped in ice veins can produce simple nucleic acids in the course of 30 years. However, I'm curious to know whether 30 years is an appropriate time frame for structure formation comparable to that in a hot environment. 30 years seems quite a contrast to the hot trigger from Urey and Miller's applied electricity. If a cold start is still questioned, the cold could've still acted as a selection factor for the common ancestral organism that gave rise to all life forms. Could that be defined as the more significant origin of life then? Well, the cold hypothesis can be quite powerful if seen in light of current exploration of possibilities of life on other worlds, i.e. Mars and various moons of Saturn. These are all very cold places!
-Bonnie Chien
Thursday, April 30, 2009
Tuesday, April 28, 2009
Evolution of the Mind
An interesting article recently surfaced in USA Today about Darwin and cultural evolution:
http://content.usatoday.com/communities/religion/post/2009/04/65672551/1
The author argues that one cannot look to Darwin to explain the evolutionary developments of the human mind. From an individual and genetic perspective, homo sapiens have not evolved that much since 50,000 years ago. (In fact, some scientists assert that there isn’t sufficient genetic variation among humans to even justify the existence of separate “races,” as 99% of our genome is the same.) So how does one explain the intellectual leaps and bounds that humans have made?
Lord Colin Renfrew of the McDonald Institute for Archaeological Research states, “If we want to know why our world is different than 90,000 years ago, we have to consider the intellectual developments that took place by following the engagement between humans and the material world.” This inquiry reminded me of Richard Klein, an anthropologist at Stanford, who argues that some neurological mutation – possibly relating to speech and the FOXP2 gene – occurred around 50,000 years ago, enabling religion, art, and culture. In other words, it wasn’t evolution per se that led to the explosion of human intellectual potential. Whatever the cause of change, it was obviously evolutionarily adaptive as it allowed Homo sapiens to dominate other Homo species and migrate to the far-flung places of the world.
If you’re at all interested in this topic, Steven Pinker writes about the Evolution of the Mind. He does not believe that changes in the brain happened “overnight” or that there was a “magical mutation.” As Pinker notes:
“I don’t think there was a thunderclap or a divine spark that suddenly made one species smart. You can see, in our ancestors, there was a gradual expansion of the brain, there was an expansion of the complexity of tools. Even when our species evolved, it surely was spread out over tens of thousands of years.”
-Alyssa Martin
http://content.usatoday.com/communities/religion/post/2009/04/65672551/1
The author argues that one cannot look to Darwin to explain the evolutionary developments of the human mind. From an individual and genetic perspective, homo sapiens have not evolved that much since 50,000 years ago. (In fact, some scientists assert that there isn’t sufficient genetic variation among humans to even justify the existence of separate “races,” as 99% of our genome is the same.) So how does one explain the intellectual leaps and bounds that humans have made?
Lord Colin Renfrew of the McDonald Institute for Archaeological Research states, “If we want to know why our world is different than 90,000 years ago, we have to consider the intellectual developments that took place by following the engagement between humans and the material world.” This inquiry reminded me of Richard Klein, an anthropologist at Stanford, who argues that some neurological mutation – possibly relating to speech and the FOXP2 gene – occurred around 50,000 years ago, enabling religion, art, and culture. In other words, it wasn’t evolution per se that led to the explosion of human intellectual potential. Whatever the cause of change, it was obviously evolutionarily adaptive as it allowed Homo sapiens to dominate other Homo species and migrate to the far-flung places of the world.
If you’re at all interested in this topic, Steven Pinker writes about the Evolution of the Mind. He does not believe that changes in the brain happened “overnight” or that there was a “magical mutation.” As Pinker notes:
“I don’t think there was a thunderclap or a divine spark that suddenly made one species smart. You can see, in our ancestors, there was a gradual expansion of the brain, there was an expansion of the complexity of tools. Even when our species evolved, it surely was spread out over tens of thousands of years.”
-Alyssa Martin
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