Trilobites, those extinct relatives of horseshoe crabs and pill-bugs, are one of the most familiar fossils. In some geologic formations, it seems that every stone examined bears another imprint of the ubiquitous Elrathia or the rather lovely Calymene. There’s no doubt that these were fairly common creatures in their day. But the reason there are so many fossils of trilobites isn’t just that there were so many trilobites. It’s because, like most arthropods, trilobites grew by shedding their old shell and spreading out a bit in a new one. Many shells could be preserved, even when the animal swam away. So for every trilobite, there can be many fossils left behind.
Vertebrates don’t share this multiple-fossil trait. They have only one skeleton to go around, and if that ends up forming a fossil, you can be pretty sure that was the end of that particular animal. Vertebrates have ways of leaving trace fossils around—a footprint here, a burrow there—and they do have several bones to scatter. But in general the rule is one animal, one opportunity to find out something about that animal through it’s remains.
There’s an exception to this rule. Unlike other animals, human beings have some replaceable hard parts. They’re called tools. While a single ancient human may have had only two hands (containing a total of 54 bones), those hands could, over a lifetime, create hundreds, if not thousands, of tools from stone, wood, ivory, shells, and animal bones. So it shouldn’t be surprising that in some locations, even many locations, the signal that humans have been there isn’t human bones, it’s human tools.
Only … there’s a problem with this. A human tooth or femur may be indisputable. So can a beautifully flaked Clovis point, or a wonderfully carved ivory fish hook. But when it comes to a stone that is only displays a few signs of “working,” is it genuinely the result of human activity, or just the happenstance of the tumbling and abrasion that happens with or without people in the vicinity? Whenever a new announcement is made about human presence in a time or place where that claim is supported only by “stone tools,” that claim deserves extreme scrutiny. And with all that in mind, here’s what appears to be an extraordinary find …
Science News: 2.4-Million-Year-Old Tools Uncovered in North Africa
Bruce Bower
Hominids used simple cutting and chopping implements to remove meat from animal carcasses in North Africa around 2.4 million years ago, archaeologist Mohamed Sahnouni and colleagues report online November 29 in Science. That’s roughly 200,000 years after the first known appearance of such tools in East Africa. Early members of the human genus, Homo, either continued to make these tools after moving from East Africa or independently created similar tools in East and North Africa, the scientists conclude.
That’s many hundreds of thousands of years ahead of previous finds, but even to a “chipped stone skeptic” this studies look pretty compelling.
Medicine
Nature: Gene-edited humans are here — Chinese scientist announced first ‘CRISPR babies’
David Cyranoski and Heidi Ledford
You knew we were going to have to talk about this one.
A Chinese scientist claims to have helped make the world’s first genome-edited babies — twin girls, who were born this month. The announcement has provoked shock and outrage among scientists around the world.
He Jiankui, a genome-editing researcher at the Southern University of Science and Technology of China in Shenzhen, says that he impregnated a woman with embryos that had been edited to disable the genetic pathway HIV uses to infect cells.
A modification that makes it more difficult for a child to be infected by HIV sounds entirely benign and reasonable. In fact, it seems likely that many parents, given the option, would wish that their child had protection from this scourge from birth. Which is exactly why, of all the science fiction dystopias that have been imagined, Gattaca is the one that seems not just possible, but inevitable.
The scientist’s claims have not been verified through independent genome testing, nor published in a peer-reviewed journal. But, if true, the twins’ birth would represent a significant — and controversial — leap in the use of genome editing. Until now, the use of these tools in embryos has been limited to research, often to investigate the benefit of using the technology to eliminate disease-causing mutations from the human germ line. But some studies have reported off-target effects, raising significant safety concerns.
The safety concerns are definitely an issue, though the most recent experiments have demonstrated ways in which the errors resulting from the use of CRISPR can be minimized. But the possibility of this technology working perfectly is perhaps a greater threat. What if it’s a gene to ensure that your child has 20/20 vision? That’s good. Proof against the causes of several cancers. Good. Free of known causes of depression? Of course. What about being a few inches taller? Well… Better looking? Smarter? This is a hard, hard — hard — technology to hold back. And the damn dam is leaking.
Science Advances: A new technique to repair heart damage and ward off attacks.
Junnan Tang, Jinqiang Wang, et. al.
On average, 635,000 Americans have a new coronary heart attack per year, which is defined as the first instance of a hospitalized myocardial infarction (MI) or a coronary heart disease death. Around 300,000 more have a recurrent attack, and an additional 155,000 experience silent MIs. Thirty-six percent of MI survivors will have an increased risk of developing heart failure down the road. To date, no approved therapy has been developed to decrease the size of an established heart scar. …
Here, we described a polymeric microneedle patch integrated with CSCs (MN-CSCs) for therapeutic heart regeneration.
Similar patches have been developed to distribute drug therapy. Here they’re being used to apply cardiac stem cells. It’s a potential “bandage for a broken heart” and while the rat and pig based testing isn’t absolutely conclusive, it’s encouraging.
Ecology
National Geographic: Whales and dolphins threatened by ‘seismic airgun’ approved by Trump
Sarah Gibbens
Five oil and gas companies have been given the green light to use seismic airgun blasts to search for lucrative oil and gas deposits that could be buried in the sea floor from New Jersey to Florida.
The proposals was nixed in 2017, but that was apparently not the right response. Now it’s been sen back and approved.
The blasts could potentially harm commercial fishing, but conservationists are particularly concerned about critically endangered North Atlantic right whales, of which only about 450 remain.
Because it’s not enough just to open more areas of the ocean for drilling. Someone had to be thinking “what can we do to really screw those damn dolphins?”
Astronomy
Science Daily: Supernova caught in formation reveals unexpected properties
Carnegie Institution for Science
A supernova discovered by an international group of astronomers including Carnegie's Tom Holoien and Maria Drout, and led by University of Hawaii's Ben Shappee, provides an unprecedented look at the first moments of a violent stellar explosion. The light from the explosion's first hours showed an unexpected pattern, which Carnegie's Anthony Piro analyzed to reveal that the genesis of these phenomena is even more mysterious than previously thought.
The type of supernova involved is the same one that’s generally used as a “standard candle” in estimations of stellar distances. It involves a massive star that explodes after capturing material from a companion star. But this is one of the few times the first moments of one of these explosions has been studied.
Archaeology
PNAS: Creatures of the grassland have been living with fire for at least 15 million years
Allison Karp, Anna Behrensmeyer, and Katherine Freeman
Fire is crucial to maintaining modern subtropical grasslands, yet the geologic and ecological history of this association is not well constrained. Here, we test the role of fire during the expansion of C4 grassland ecosystems in the Mio-Pliocene through innovative molecular proxies from ancient soils in Pakistan. We produce a synoptic terrestrial record of fire and vegetation change in this region, which indicates that increased fire occurrence accompanied two stages of landscape opening. Proxy data confirm that a pronounced fire–grassland feedback was a critical component of grassland ecosystems since their origination and fostered the rise of C4-dominated grasslands. The approach presented here can be used to examine landscape-scale interactions between paleofire and vegetation for other geographic regions and climatic transitions.
The grasslands don’t just cope with fire. They’re made by fire. Grasslands might even be said to be the mark of a set of organisms that have evolved to encourage fire in order to maintain an open, relatively treeless environment.
Nature: Tibet was the last part of Asia to be inhabited by humans
Jia-Fu Zhang and Robin Dennell
By 30,000 years ago, humans had colonized almost every part of Asia that was not covered by ice sheets and may even have settled on the shores of the Arctic Ocean. One of the last places in Asia that was colonized was the Tibetan Plateau, one of the most challenging and hostile environments of the Northern Hemisphere. With an average elevation of about 4000 m above sea level and an average annual temperature close to the freezing point of water, and with only half the concentration of oxygen as at sea level, it is not hard to see why it was such a challenge.
It’s amazing that people inhabit the area in numbers today. But maybe in the Ice Age, it was just higher ice.
Climate
Nature: What happens at one pole, doesn’t stay at one pole.
Nerilie Abram
Past rapid warming events in the Northern Hemisphere give researchers a way of addressing fundamental questions in climate science. In particular, how do changes in the climate of one hemisphere affect that of the other? And how, and at what rate, do these changes propagate? The connection between hemispheres is important for determining how energy moves through the Earth system and alters the climate in different places around the globe.
As it turns out, there are surprisingly direct connections between what’s happening at the “top” of the world and what goes on at the “bottom.” Ocean currents carry changes from one end of the planet to the other, so that changes in ice and temperature in the Arctic can almost immediately affect wind, precipitation, and temperature all the way in the Antarctic.
Geology
Science: Large impact crater under Greenland potentially dates from around end of Ice Age.
Kurt Kjær, Nicolaj Larsen, et. al.
We report the discovery of a large impact crater beneath Hiawatha Glacier in northwest Greenland. From airborne radar surveys, we identify a 31-kilometer-wide, circular bedrock depression beneath up to a kilometer of ice. … Geochemical analysis of this sediment indicates that the impactor was a fractionated iron asteroid, which must have been more than a kilometer wide to produce the identified crater.
Note that while this is sure to boost the “asteroids did in the mega-fauna” fans, the dates on this impact aren’t clear, there were many other impacts in this range without identified large species loss, and the impact still doesn’t explain the disappearance of megafauna from different areas at different dates.
Image
The image this week is from Andy Brunning at Compound Interest. Visit his site for a larger, easier to read version. And yes, I’ve used this one before. Starting next week, look for the new version of Andy’s Chemistry Advent Calendar.