Ancestor of All Placental Mammals Revealed 123
sciencehabit writes "The ancestor of all placental mammals—the diverse lineage that includes almost all species of mammals living today, including humans—was a tiny, furry-tailed creature that evolved shortly after the dinosaurs disappeared, a new study suggests. The hypothetical creature, not found in the fossil record but inferred from it, probably was a tree-climbing, insect-eating mammal that weighed between 6 and 245 grams—somewhere between a small shrew and a mid-sized rat. It was furry, had a long tail, gave birth to a single young, and had a complex brain with a large lobe for interpreting smells and a corpus callosum, the bundle of nerve fibers that connects the left and right hemispheres of the brain. The period following the dinosaur die-offs could be considered a 'big bang' of mammalian diversification, with species representing as many as 10 major groups of placentals appearing within a 200,000-year interval."
Re:More Info Please... (Score:3, Informative)
We're starting to sequence the genomes and map species after species at an accelerating rate. Within the century we'll have a gene-by-gene map of the ancestry of most of the biosphere.
Re:No intermediate steps to prove! (Score:5, Informative)
Within the past 200,000 years of human history, we're aware that Homo Sapiens Sapiens existed alongside other members of the Homo genus, including Homo Neanderthalis and Homo Floresiensis.
Re:More Info Please... (Score:5, Informative)
science doesn't deal with facts
Uh, what? Facts are the foundation of science. If science has any issue with facts it's that Joe Sixpack thinks the hierarchy is...
Hypothesis -> Theory -> Facts
In actuality, it's...
Facts -> Hypothesis -> Theory
Hypotheses and theories are built on facts. Maybe you meant science doesn't deal with proof?
Re:More Info Please... (Score:4, Informative)
The characteristics of the first placental are not really controversial. The real news here is that a lot of the work on placentals and eutherians is wrong and must be re-evaluated. Granted, a lot of the placental work was already merely tentative. Molecular phylogenetics estimates had placentals appearing about 105 Mya, This new work ignores the molecular results and comes up with a later date. From what I can see, dating of the relevant available fossils is equivocal.
Also curious is that according to this interpretation, the ancestral afrotherian (elephants, aardvarks, manatees, etc.) originated in South America and somehow migrated across the then 1000-mile ocean to Africa. Prepare for further revision.