I trace my ancestry to Snowball Earth<\/p>\n
Durbin, Orin Lole et al. \u201cRe-evaluating molecular clock maximum age calibrations revives pre-Ediacaran divergence estimates for animals.\u201d Science Advances.<\/a><\/p>\n When did the first animals emerge on Earth? It\u2019s a question that has provoked centuries of scholarly debate, and also inspired some wonderful answers in myth and legend (I\u2019m partial to the Bible\u2019s tidy solution: day six checklist).<\/p>\n The earliest animals that are clearly preserved in the fossil record lived during the Ediacara period some 574 million years ago, but the origins of our diverse metazoan family are likely much older. Now, scientists suggest that animals may have appeared on Earth a whopping 800 million years ago, during the ancient Tonian era, according to a new estimate of the dawn of animals.<\/p>\n \u201cThe timing of the origin of animals on Earth has puzzled scientists for centuries,\u201d said researchers led by Orin Lole Durbin who was at the University of Oxford during this research and is now at Virginia Tech. \u201cUnambiguous animal body fossils within the Ediacara Macrobiota provide a hard minimum calibration of 574 [million years] for crown Metazoa. Animals must have evolved before this date. Determining a maximum calibration for animals (a date at which they had not yet evolved) is a more complex task.\u201d<\/p>\n Estimated timeline for the origin of animals based on molecular clock analyses. The grey bar on the right of the image is the origin of animals based on an Ediacaran upper calibration. The grey bar to the left is the origin based on older deposits in the Tonian period, as suggested by the new study. Image: Orin Lole Durbin.<\/p>\n The team turned to molecular clock analysis, a technique that uses the rate of genetic mutations in lineages as a rough way to reconstruct evolutionary timelines. The researchers focused on two fossil deposits\u2014China\u2019s Weng’an Biota and Mongolia\u2019s Kheseen Biota, which date back 590 and 550 million years respectively\u2014to extend the possible timeline of animals back more than 200 million years earlier.\u00a0<\/p>\n If animals really did appear in the Tonian era, it means that our earliest metazoan ancestors survived episodes of so-called \u201cSnowball Earth,\u201d when our planet was almost fully covered in ice. These early critters were likely simple marine sponges and comb jellies that lived for hundreds of millions of years until their descendents exploded into the kaleidoscopic variety of animals that persist to this day.<\/p>\n \u201cThe possibility of a pre-Ediacaran origin and diversification of animals means we cannot discount hypotheses that link the timing of animal diversification to Cryogenian Snowball Earth glaciations,\u201d according to the study. \u201cThe causes and trajectory of animal evolution will remain uncertain until paleontological and geochemical data provide sufficient confidence in maximum calibrations to ensure a reliable timescale.\u201d<\/p>\n In short: Respect your sponge elders.\u00a0\u00a0<\/p>\n In other news\u2026<\/p>\n A pole-ing error<\/p>\n Domeier, Mathew et al. \u201cQuadrupolar sea level fluctuations reveal episodes of rapid polar wander.\u201d Science.<\/a><\/p>\n Earth is a roiling mess of shifting continents and squishy innards, a situation that constantly throws its spin axis off balance and prompts the geographic poles to drift. This phenomenon, known as true polar wander (TPW), is distinct from Earth\u2019s wandering magnetic poles, which are shaped by interior core-mantle processes.\u00a0<\/p>\n Right now, TPW is clocked at a slow rate of 10 centimeters per year, but scientists have found evidence of \u201cfast\u201d episodes of TPW that pushed the poles off by thousands of miles over millions of years, which has knock-on effects for ocean and land distribution across the globe.\u00a0<\/p>\n A team has now pinpointed several of these fast episodes over the past 320 million years, \u201cconfirming that protracted rapid TPW has occurred on Earth and that couplings among Earth\u2019s rotational dynamics, mantle processes, and surface environments can be strongly episodic,\u201d according to their study.<\/p>\n \u201cThese findings refute the view of TPW as negligible or persistently slow and highlight the need to consider TPW as an episodic control on sea level change and likely other global environmental and biological dynamics,\u201d said researchers led by Mathew Domeier of the University of Oslo.\u00a0<\/p>\n In addition to these long-term natural changes, recent human activity has slightly impacted TPW<\/a>, especially the construction of dams and the glacial melt of anthropogenic climate change. So the next time you address a letter to Santa at the North Pole for your kid\u2014or yourself, no judgement\u2014make sure you have the most up-to-date coordinates.<\/p>\n It\u2019s raining formaldehyde\u2014formalallelujah!\u00a0<\/p>\n Koyama, Shungo et al \u201cGlobal Distribution of Atmospheric Formaldehyde Deposition Correlated with Water Vapor on a Warm Early Mars.\u201d The Planetary Science Journal.<\/a><\/p>\n Formaldehyde, the toxic chemical, has a bit of a morbid reputation\u2014exposure to it can be fatal and it\u2019s a common ingredient used to embalm corpses. But, paradoxically, formaldehyde (H2CO) also helped pave the way for the emergence of life on Earth as a precursor of bioessential elements such as sugars, amino acids, and nucleobases.<\/p>\n If life ever flourished on Mars, formaldehyde would likely also have been part of the story. To map out the possible distribution of the chemical on ancient Mars, scientists ran models of its atmosphere between 3.6 and 3.8 billion years ago, when the red planet was warmer and wetter. The results showed that formaldehyde was strongly associated with water vapor, suggesting that the chemical rained down from the ancient skies into Martian waterways.<\/p>\n \u201cSignificant atmospheric deposition of H2CO is observed over water bodies, including the northern ocean,\u201d said researchers led by Shungo Koyama of Tohoku University. \u201cWe suggest that basins adjacent to persistently humid regions, which likely experienced H2CO accumulation and subsequent organic synthesis, could be potential landing sites for future missions to investigate ancient chemical evolution and whether it led to the origin of life.\u201d<\/p>\n Hopefully, future missions to Mars will leave any signs of life with no place left to formalde-hide.\u00a0<\/p>\n Update the cosmic actuary tables<\/p>\n<\/p>\n