March 03, 2018 at 04:26AM

Today I learned: 1) Cave bacteria! There are bacteria that live exclusively on the inside surfaces of cave rock. They form visible sheets, and sometimes excrete really pretty minerals. I don't know much about them, but they can somehow live off of the rock face -- I'm not sure whether they're filter-feeding stuff that comes by, or if they're actually reacting the rock for energy. Whatever they're eating, it's not a particularly *accessible* source of food -- they are VERY SLOW GROWING, taking decades to fill small gaps in their mats. Some kind scientists at University of New Mexico compared the community compositions of cave bacteria and soil bacteria (http://ift.tt/2F8VxVa). Their conclusion was that the broad distribution of taxa was quite similar in the caves and in the soil above, but that there was quite a bit of divergence between *species* in the two climes. In other words, it looks like all of the usual inhabitants of soil got into the caves and colonized with roughly the same success, but then they evolved to look pretty different from their above-ground ancestors. Thanks to Patricia Prewitt for tipping me off to the existence of these critters! 2) RAND corporation has a new meta-study on the effects of gun policy. I've only read their summaries, but it looks pretty comprehensive. The big take-away is that there isn't enough data to make strong conclusions about most questions around the effets of gun control. There isn't a ton of data on gun violence, and what data there is isn't sufficient to reliably detect small effect sizes (which could still add to thousands of deaths per year). None of this is surprising, since the US government is BARRED BY LAW FROM FUNDING RESEARCH ON GUN CONTROL. It's usually not a good sign if someone feels they have to ban research on a topic, especially a poitically-charged one. Frankly, I don't take much of a hard stand on gun control one way or another, but IMHO the current research climate on gun control reeks of Lysenkoism. ANYWAY, the second-biggest take-away from the RAND meta-study is that there are *some* policies that appear to be effective at reducing violent crime, accidental deaths, and suicides (especially suicides). The first figure at this link is a good summary (http://ift.tt/2HYu9uF). For those who prefer a written digest, here it is: background checks and child access prevention laws help reduce suicides pretty dramatically; child-access prevention laws also almost certainly reduce accidental gun deaths; background checks and mental health screening probably decrease violent crime, and (perhaps surprisingly) stand-your-ground laws probably *increase* violent crime; concealed-carry laws might increase both accidental and homicidal deaths from guns, but the evidence is weak; most surprisingly to me, there is not evidence that bans on assault weapons and high-capacity magazines have much effect at all on anything. You can read the rest of the report here, if you're super-interested in gun control research and you have a lot of time on your hands: http://ift.tt/2t87FE9 3) Cells in a developing embryo can detect their position within the embryo within about 1% error, we think only using the concentrations of four transcription factors that are distributed in specific ways around the embryo. We don't know exactly how they do it, and that's quite close to the inforamtion-theretical limit of precision for the amount of information available in those transcription factor signals (unless, of course, there are channels they're exploiting that we don't know about). Thanks to Andy Halleran for this one!