ريتشارد دوكنز's Blog, page 687
September 17, 2015
Check Out This Seal Riding A Whale
Photo credit:
Robyn Malcolm
Talk about a sweet deal. Not only did this lucky seal get the best seat around the metaphoric dinner table, but it was also treated to a fresh banquet unwittingly served by a pod of humpback whales busy on a fishing trip.
Homo naledi—Another Awesome Twig on the Human Family Tree, Part 2
In Part 1, I described the totally serendipitous discovery of an unprecedented hominin fossil haul. More than 1,500 bones of at least fifteen individuals (representing both genders and ages ranging from infant to elderly) of a new hominin species were pulled from an extremely difficult-to-get-to cave in South Africa. When we left off, more than fifty scientists had just finished a six-week fossil identification and sorting party and we were getting ready to unveil Homo naledi and explain why one paleoanthropologist called it “weird as hell.”
The 737 partial or complete anatomical elements that make the official description of Homo naledi. The “skeleton” in the center is a composite of elements that represent multiple individuals. This view is foreshortened; the table upon which the bones are arranged is 120-cm wide for scale. (Lee Roger Berger research team - http://elifesciences.org/content/4/e0.... Licensed under CC BY 4.0 via Wikimedia Commons)
I think I’ve used the following phrase before, but it’s worth repeating. Evolution results in a mosaic of traits. It’d be nice and neat if traits evolved in a set order, so that every species of a certain slice of geologic time has Trait A, then all subsequent species have traits A and B, and then A, B, C, and so forth. But instead you get a hodgepodge. Once species has traits A, E, and G while a contemporary species has A, B, T, and P. Then a later species has E, T, Q, and R…. well, you get the idea. It’d be great if trait distribution in the fossil record told a nice, neat story, but it doesn’t—and if it seems to, it’s only because the fossil record is incomplete, and it’s easy to draw a straight line if you only have a few data points.
Homo naledi’s foot is so much like our own, that one researcher said that if you found an H. naledi foot in isolation, you’d assume “some bushman had died.” (Lee Roger Berger research team - http://elifesciences.org/content/4/e0.... Licensed under CC BY 4.0 via Wikimedia Commons)
But when the team tried to plot Homo naledi on the map of hominin evolution, things got more than messy—they got perplexing. H. naledi has some features that are very modern, including feet that apparently are indistinguishable from our own. The shoulders, however, are more similar to early hominins like the famous Australopithecus afarensis, “Lucy.” Then there are “schizoid” parts of the body that are a hybrid of modern and ancient. The top of the hips, for example, resembles an Australopithecus, but the bottom of the pelvis looks modern. In their mouths, H. naledi had modern molars but “weirdly primitive” premolar roots. The hand bones were modern, but the fingers were long and curved, seemingly well adapted to climbing. In general, there seemed to be enough “modern” to place the find within the Homo genus…but there is one problem.
Reconstructed H. naledi skull (composite) with estimated cranial volume of about 466cc—modern human brains are more like 1200cc. (Lee Roger Berger research team - http://elifesciences.org/content/4/e0.... Licensed under CC BY 4.0)
“It has a tiny head. People expect species from the Homo genus to have bigger brains.” That’s what my friend and paleoanthropologist Briana Pobiner told me when I asked her about H. naledi. Jamie Shreeve, in his excellent piece for National Geographic, described it this way: “These were pinheads, with some humanlike body parts.” How tiny were their brains? Well, remember how I said some paleoanthropologists were unhappy with H. habilis being within our genus because its brain is about half the size of ours? H. naledi has an even smaller brain.
So it seems we might have to give up on “big brains” being the hallmark of our genus. But that’s not the only tough pill scientists have to swallow. Remember how these bones were found in a cave accessible only to super-tiny super-scientists and spelunkers? How’d they get there? And why were there so many bones all together? The latter question has an easier, albeit surprising answer. There were no teeth marks on the bones, so scientists have eliminated the possibility of the bones being dragged to the cave by predators. Besides, you would assume predators would drag other animals into the cave, too. They have also eliminated the idea that the hominins lived in the cave, since there was no evidence of stone tools or anything else that would suggest habitation. And finally, the bones are distributed in such a way as to make it highly improbable that the hominins got trapped. So you eliminate all of those possibilities and what are you left with? H. naledi was dumping their dead—deliberately and repeatedly potentially over centuries. This is different from saying that they buried their dead—there is no evidence of ceremony or ritual—but there is still some sophistication to this process. Why’d they do it? Pobiner says: “Dead people smell bad and attract predators. A cave would be a good place to keep them far away from where you hang out, too, so I can see chucking bodies into the cave so you wouldn’t be the next one eaten for dinner.” (Can you guys tell why she’s my friend?)
The distribution of the different geological units shown together with the inferred distribution of fossil material in the Dinaledi Chamber. The fossils came into the cave via the chamber entrance at top right. Unit 1 represents early sediments that contain only some rodent fossils. Unit 3 represents rubble sediments containing most fossil bones. Note that the excavation area is only a tiny portion of the cave—there is much more to find. (Paul H. G. M. Dirks et al - http://elifesciences.org/content/4/e0.... Licensed under CC BY 4.0 via Wikimedia Commons)
Okay, so they were chucking bodies into the cave…but how? The easy answer would be that the cave was once directly accessible from the surface—but there is no evidence to support that. There are no bones from other organisms, for example, that would surely have fallen in or gotten trapped were there an entrance to a giant cave along the ground. There are also no plants or rubble that would have certainly washed in from the surface. So they must have climbed down into the cave, through (presumably the then-wider) Superman’s Crawl to drop the bodies down the chute and into the cavern where they were found. Why is this a difficult pill to swallow for some? Because there is no way the H. naledi could have completed that trip without some light—they must have had torches. And for some, the idea that a tiny-brained creature could do that is just too difficult to accept. Paleoanthropologist Richard Leakey (son of Louis and Mary), for one, doesn’t buy it. “There has to be another entrance. Lee [Berger] just hasn’t found it yet.”
Geologists say no, however. There was no other entrance. Eric Roberts said simply, “There isn’t a lot of subjectivity here. The sediments don’t lie.”
Sediments might not lie, but they aren’t always as informative as you want them to be, either, which brings us to a big problem with Homo naledi… to be discussed in Part 3.
Are you a teacher and want to tell us about an amazing free resource ? Do you have an idea for a Misconception Monday or other type of post? Have a fossil to share ? See some good or bad examples of science communication lately? Drop me an email or shoot me a tweet @keeps3.
September 16, 2015
The Hunt For the Fat Gene
Medical researcher Richard Johnson, of the University of Colorado Anschutz Medical Campus, talks about his October Scientific American article The Fat Gene, co-authored by anthropologist Peter Andrews of University College London and the Natural History Museum in London. Their piece is about how a genetic mutation in prehistoric apes may underlie today’s pandemic of obesity and diabetes.
Kim Davis: Kentucky’s Martyr For Bigotry
Kim Davis. Is she a hero or hypocrite? She continues to refuse marriage licenses to same sex couples despite the Supreme Court ruling in favor of gay marriage. Mike Huckabee jumped into the spotlight too, because he really really cares about Kim Davis #ImWithKim -_-
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Kim Davis and Mike Huckabee made a spectacle of themselves. She’s operating under God’s Authority not to issue marriage licenses, so legally she’s safe right? NO! Kim Davis has a job, and she’s not doing it. The judge sent her to jail and held her in contempt of court. She still managed to give a speech as she returned to work, asking why people won’t accommodate her deeply held religious beliefs. She’s being called a hero and compared to MLK. The Christian persecution complex has a new poster girl, Kim Davis.
Amazon Founder’s Rocket Company Will Be Launching From Florida
Photo credit:
Blue Origin tested a sub-orbital rocket in April this year. Blue Origin.
The private space race is getting heated, with companies like SpaceX and Orbital Sciences in the U.S. making huge strides in recent years. And now, Amazon founder Jeff Bezos has thrown his hat firmly into the ring, with the announcement of a new launch facility at Cape Canaveral in Florida.
Why You Should Stop Using Antibacterial Soap
Photo credit:
Many antibacterial soaps contain the potentially harmful chemical triclosan. Brian A Jackson/Shutterstock
Antibacterial soaps containing the chemical triclosan are no better at removing bacteria from your hands than conventional soaps, a new study has concluded. This raises questions about the necessity of using the chemical, which has been labeled as potentially dangerous, in antibacterial soaps.
Shift In Human Ancestors’ Diet Earlier Than Previously Thought
Photo credit:
Early humans, such as Lucy (pictured), probably started eating grass-based diets around 3.8 million years ago. Carlos Lorenzo/Flickr CC BY-NC-ND 2.0
The shift that our ancestors made from relying mainly on trees and shrubs for food, to searching for grub on the ground and eating more of a grass-based diet could have helped them fare better in a changing environment. New evidence points to this event occurring much earlier than was previously thought – about 400,000 years earlier, to be precise.
Is the Alzheimer’s protein contagious?
LEONARD LESSIN/SCIENCE SOURCE
By Emily Underwood
Beginning in 1958, roughly 30,000 people worldwide—mostly children—received injections of human growth hormone extracted from the pituitary glands of human cadavers to treat their short stature. The procedure was halted in 1985, when researchers found that a small percentage of recipients had received contaminated injections and were developing Creutzfeldt-Jakob disease (CJD), a fatal neurodegenerative condition caused by misfolded proteins called prions.
Now, a new study of the brains of eight deceased people who contracted CJD from such injections suggests that the injections may also have spread amyloid-β, the neuron-clogging protein that is a hallmark of Alzheimer’s disease. The study is the first evidence in humans that amyloid-β might be transmissible through medical procedures such as brain surgery—according to the researchers. Skeptics, however, note that the CJD prion itself often triggers unusual amyloid deposits; epidemiological studies, they say, find no connection between the injections and increased risk of developing Alzheimer’s disease.
Aside from CJD and the related mad cow disease, kuru is perhaps the most famous prion disease. Endemic to Papua New Guinea and now essentially eradicated, kuru is transmitted through the ritual consumption of human brain tissue at funerals. Increasingly, however, scientists are recognizing that a number of other neurodegenerative diseases, including Alzheimer’s, Huntington disease, and Parkinson’s disease, also involve aberrant proteins that act like “seeds” in the brain. They convert otherwise normal proteins into fibers that “break, form more seeds, break, and form more seeds,” says John Collinge, a neuropathologist at University College London and lead author of the new study.
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Elon Musk to Stephen Colbert: Nuclear Weapons Could Terraform Mars
YouTube
By Sarah Fecht
Elon Musk has often been compared to Tony Stark. The billionaire entrepreneur is the brains behind SpaceX’s reusable rockets, Tesla’s electric cars, and the solar power provider SolarCity. But last night when comedian Stephen Colbert pressed Musk to decide whether he’s a superhero or a supervillain, Musk was evasive.
Now we know why. Later on in the interview, Musk admitted that he advocates detonating thermonuclear explosives on neighboring planet Mars.
The businessman has often stated that he thinks humans should colonize Mars, and now it seems he’ll stop at nothing to get his way.
“It is a fixer-upper of a planet,” Musk told Colbert. “But eventually you could transform Mars into an Earth-like planet.”
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Researchers Develop Implantable Device That Soaks Up Cancers Cells
University of Michigan Engineering
By Victor Johnson
Researchers at the University of Michigan have developed a new implantable device designed to soak up cancer cells wandering throughout the body and according to Michigan Engineering’s Gabe Cherry, it could eventually be used to slow the spread of the deadly disease between the body’s organs.
Thus far, researchers have only tested the implant in mice, however it seems to stop wandering cancer cells from reaching other areas where new tumors could form. If this proves to be the case with humans implanted with the sponge-like device, it could be really good news for cancer patients as the BBC reports that according to Cancer Research UK, 9 out of 10 cancer deaths were caused by the disease spreading to other parts of the body.
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