I got a giggle from reading Larry (and then John Hawks) talking about time travel. Kinda. I mean, people using science to look back in time, and orient themselves in that different era to such a degree they can gain information about said time.
Scientists arent just guessing when they estimate when humans and chimpanzees split into different species, or where/how ‘new’ species like Ardi and Teh Hobbit fit into the tree– they are using two totally different arms of science figure out how species were oriented millions of years ago. We have estimates from fossils and how old they are and when/where we find them (estimates based on geology, anthropology). And then we have molecular clocks (estimates based on biochemistry, genetics).
These methods arent mutually exclusive– I think its normal to use fossils to ‘calibrate’ molecular clocks. The more info we have, the easier it is to see back in time.
But sometimes these two methods do give ‘answers’ that are too different for scientists (Larry):
The theoretical models agree on a human-chimp divergence time of 3-5 million years.
I’ve been skeptical of the fossil record calibrations for many years because they give some very unreasonable divergence times and because the so-called “fixed” standards also seem unreasonable. The molecular clock ticks at an approximately constant rate but we just don’t know what that rate is. I would have no problem accepting that humans and chimps diverged 6-7 million years ago.
Okay, so why did this make me giggle?
We kinda have the same issues with HIV-1. A LONG TIME AGO, in THE YEAR 2000, we thought HIV-1 crossed into humans 1931 (1915 – 1941).
Then ALL THE WAY BACK IN 2008 we found another ‘fossil’– HIV-1 from 1960. They used that fossil to recalibrate HIV-1s clock, and then the speciation event got thrown back to 1921 (1908 – 1933).
So as I was reading their posts, nodding and thinking ‘Ya, I totally know what theyre talking about’, the absurdity of comparing an event that happened millions and millions of years ago to an event that happened ~90 years ago made me lol.
LOOKING THROUGH THE SANDS OF TIME ALL THE WAY BACK TO 1921!!! THEY BARELY HAD MILITARY AIRCRAFT IN 1921!! One estimate was as low as 1873… OMG I CANT EVEN IMAGINE A WORLD WITHOUT COORS LIGHT! WHAT AN ALIEN TIME!
hehehehe 100 years ago, 5 million years ago, same thing