Evolution of Mammals Re-evaluated

AaxelB writes "A study described in the New York Times rethinks mammalian evolution. Specifically, that the mass extinction of the dinosaurs had relatively little impact on mammals and that the steps in mammals' evolution happened well before and long after the dinosaurs' death."

Comments

Re:Evolution? I thought Jebus created the dinosaur

[rucs_hack]

I thought it was about six million years, could be wrong though.

The big thing was grass, it hadn't been around for most of the time the dinosours had existed. The domination of grasses after the CT event really helped the spread of species

Re:This is Great

[Coryoth]

Until the next "re-thinking." Will we ever have hard evidence, or just thought experiments? But we do have hard evidence - indeed it was hard evidence that helped lead to this rethinking. Recently there have been a number of finds of surprisingly large mammals that are much older than had previously been expected. They include a beaver like (pre)-mammal from the Jurassic that was almost half a metre long, discovered in 2004, and two species large carnivorous mammal from the cretaceous (dated to about 130 million years ago - or 65 million years prior to the dinosaur extenction) which were discovered in 2000 and 2005. Such large mammals (relatively speaking) during the time of the dinosaurs draws into question the previous belief that mammals were restricted to small rat/mouse like scavengers at that time. Instead we see evidence of large, active, meat eating mammals. This implies that mammals were rather less marginalised during the dinosaurs "reign" than previously thought, and imples that mammal evolutionary history needs to be rethought accordingly.

Many mammalian lineages predate the K-T extinction

[saforrest]

If you read The Ancestor's Tale by Richard Dawkins, you'll find that recent genetic evidence suggests that many of the distinct branches of modern mammals predate the K-T extinction.

In particular, by the time of the K-T extinction, I believe that the primate lineage had already separated from rodents, as well as the laurasiatheres (all hoofed mammals, lions, tigers, bears, etc.), xenarthrans (armadillos, sloths, etc.), and afrotheres (elephants, manatees, anteaters, etc.).

So, while most mammals in the Cretaceous may still have been tiny shrew-like creatures scurrying around in the underbrush, many of the modern lineages had already come into separate existence.

It is also interesting to read, in the book, that our nearest non-primate relatives aside from the tree shrews are rodents. I can sort of see it: give a mouse a little more finger dexterity and it wouldn't not that different from a lemur. It also might explain why rodents are such good laboratory specimens.

Re:Shamelessly off-topic, but must be done...

[Daniel Dvorkin]

There is obviously no evidence that the mutations which gave rise to speciations were "random" and not in some way directed, naturally or supernaturally, or otherwise forced in some particular direction.

"Obvious" if you ignore pretty much all work in molecular genetics at least since Watson and Crick.

Once we arrive at a better understanding of how DNA works, perhaps it will be possible to form mathematical models to determine whether or not the "random mutation" theory is feasible.

You mean, the way bioinformaticists and statistical geneticists do all the time, right now, and have been for years?

Maybe it's only feasible during intermittant radiation events that decimate populations by causing widespread mutations, leaving a few individuals with improvements, who go on to reproduce and build up populations again. Maybe it's not possible at all.

Do you have any data, at all, that would support either one of these hypotheses? Or are you just cut'n'pasting from some ID site somewhere?

Re:Surprise, but not a showstopper

[testpoint]

I have recently examined the Marzeah Papyrus (7th century B.C.), fragments of the dead sea scrolls, septuagint leviticus , septuagint exodus and Gospel of John fragments all from the 3rd century A.D. Modern, nonparaphrased, versions of the Bible, corresponding to these fragments are accurately translated.

Many of the original writers and earliest translators could write and speak multiple languages. While you might consider them superstitious they weren't illiterate. William Tyndale, a 16th century scholar and translator was fluent in eight languages. His work influenced Shakespear and the King James version of the Bible.

Tyndale was strangled and burned at the stake because a version of the Bible that could be read by all, transferred power from the King and the Pope to the church, which Tyndale translated as congregation or congress (people) rather than church (hierarchy). Many credit Tyndale and his translation for furthering the concepts of representative democracy, individual responsibility, and equality.