Thread: flying lemurs are our closest relatives!

In an article in Science magazine researchers looked at the evolutionary relationships between primates as a group and the flying lemurs (who aren't lemurs) and tree shrews.

It always has been a bit unclear who our closest relatives are; tree shrews or flying lemurs?

Their molecular data says with confidence that it is the flying lemurs!

Welcome cousins.

Not that the tree shrews are far away from our lineage either.

A Bayesian relaxed molecular clock approach with eight fossil constraints estimated the origin of Euarchontoglires at 88.8 million years ago (My), Euarchonta at 87.9 My, and Primatomorpha at 86.2 My

The glires are of course rodents and rabbits. They split from the primate lineage (or we split from the rodent lineage) 88.8 million years ago. And only a million years later the Eurarchonta split off, the lineage that would give rise to tree shrews. And then another million years or so later the whole primate lineage split off from the lineage that would give rise to the flying lemurs.

It was all happening deep in dinosaur territory. And basically in a short geological timespan.

And then the great radiation of mammalian species could start!

reference:
http://www.sciencemag.org/cgi/conten...t/318/5851/792


ps. ophiolite, i can assure you this isn't my homework! :wink:

some pictures to make it more tangible.

Our cousin the flying lemur.



a tree shrew.

The one on the top looks just like my aunt, so I'm convinced.

I never knew the splits were that far back. Interesting stuff.

our ancestor looks a bit like a cross between a flying lemur, a tree shrew and a shrew.

here is a shrew:



It's all quite interesting though because we use mouse models for human biology. And they split off 80+ million years ago, and their ancestor looked like a shrew. Which may resemble superficially like a mouse, but it is actually totally different.

It's good stuff this evolution. It makes your head spin once you start thinking about what everything really means.

Originally Posted by spuriousmonkey

It's good stuff this evolution. It makes your head spin once you start thinking about what everything really means.

That's why I love it so. =)

Evolution = thought in process

From one thought evolves another and so on and so forth

life = a living thought

energy = life = thought = energy

we think and therefor we are

Are we the only primates with opposable thumbs?

Originally Posted by samcdkey

Are we the only primates with opposable thumbs?

no. most, if not all (i'm not exactly sure) primates have opposable thumbs. it's for gripping trees while climbing and manipulating fruit.

Originally Posted by samcdkey

Are we the only primates with opposable thumbs?

Dolphins (though not primates) have them too.

Dolphins have thumbs? let alone opposable?


/hi Tor :-D /

Originally Posted by samcdkey

Dolphins have thumbs? let alone opposable?


/hi Tor :-D /

Nope, but they do have little skeleton hands under their flippers!

or do theyyyyy have ooposable thumbs
http://www.theonion.com/content/node/28315

It says here:
"A primitive axe crafted out of driftwood and shell that is believed to be the handiwork of dolphins."

My first ever (science) post on sciforums was about 'dolphin hands' lol

memoriesss

I've seen them wave the flippers, but haven't seen them give a thumbs up.

Oh dear! Douglas Adams must have known about this! Anything similar happen with mice by any chance? :?

This recalls to mind the title of an article published in the comedic newspaper, the Onion: "Dolphins Evolve Thumbs, 'Oh Shit' Says Humanity"

A dolphin with extra limbs. A bit off topic, but I found it googling and thought it was interesting.

http://www.edwardtbabinski.us/whales/hind_limb_buds/

The previous post mentioned an article on dolphin limb development. I shall try to translate it a bit in more popular terms. Or at least give the most important findings.

Limbs grow from a tiny structure on the fetus called the limb bud in all tetrapods.

As you can imagine there would be several ways to get rid of a hindlimb (as is the case in the dolphin).

1. You could prevent the limb bud from forming.
2. You could let it form but never really develop much.
3. You could let it develop and then reduce it later in life. It is often easier in development to eliminate a structure by means of cell death then to prevent creating it.

This article studied this exact topic.

They found that the hind limb buds do form in the dolphin. So that eliminates option no.1.

In most developing organs there is a little substructure called 'organizer'. It is a small cluster of cells that express signaling molecules that instruct the surrounding tissue to do their 'stuff'; grow, die, differentiate.

In the limb there are two; the Zone of Polarizing Activity or ZPA. And the Apical ectodermal Ridge or AER.

The ZPA is most famous for expressing the signaling molecule SHH (sonic Hedgehog - named after the game character). It's absent in the Dolphin hind limb bud.

The limb bud does seem to have an AER that expresses the signaling molecule FGF8 (Fibroblast growth factor 8 - there are more than 20 and these molecules are known to stimulate growth of many cell types, not just fibroblasts. It was just originally discovered as a fibroblast growth factor). But the AER and Fgf8 expression are just not maintained.

The paper suggests that the loss of SHH might have been gradual, that is, it's expression has been shortened during evolution, eventually leading to total absence.

By shortening the duration of the expression the ZPA as an instructive signaling center is active for a shorter time.

Since first the proximal structures are laid down this means that shortening of the duration of SHH expression will first lead to a loss of distal structures. (proximal is near the body, distal is towards the tip of the limb - upper arm is proximal, hand is distal)

Don't know about that last conclusion though. It's more speculation than fact.

http://www.pubmedcentral.nih.gov/art...?artid=1482506