View previous topic | View next topic

Marsupials ARE mammals Steven!!

Page 2 of 2
Goto page Previous  1, 2

27248.  Tue Oct 18, 2005 8:20 am Reply with quote

I'm not sure of the current state of the 'out of Africa' theory but Australia has been inhabited for somewhere between 40 000 and 60 000. Human remains were found in Lake Mungo in 1974, so he was dubbed "Mungo Man".

27450.  Wed Oct 19, 2005 2:15 pm Reply with quote

Hey guys - actually I am reasonably up to date on this. Heard from Spencer the week before last (he of the project discussed in the article Carl quotes). He was about to leave for 7 weeks in Chad for the below.
Carl wrote:

Our lot of Homo Sap 1st left Africa around 100,000 years ago, and fanned out, following the then coastline - the sea is now around 250m higher than it was then. Spot on about the Andaman Islanders - who are very closely related to the San/Bushmen of the Kalahari. The Bantu of west Africa were better breeders and pushed them into a corner of their former territory just through sheer numbers. We have supporting evidence from the complexity of their 'click' language. Extremely complex (41 sounds, if I remember rightly) so long time to develop.

There were earlier migrations out of Africa (Homo Erectus - the Neanderthal mystery, etc) but they all died out. All the polymorphisms of the various Y chromosomes today can be traced back to one chap 100,000 years ago - ie a single chap before he left. It's a theory that's grounded in hard evidence, and Spencer's racing round the world collecting samples before we all migrate to such an extent that once again we become one. As he says, a Friday night in an upper West side night club is a breeding pool that probably includes most of the genetic rainbow.

There's loads more, but this is turning into a monologue...If he has time next time he's in the UK, perhaps it would be fun to do something at the club? If you want to read something I'd rec his book - The Journey of Man - even over and above Jared Diamond. It's extremely accessible, too.

27579.  Thu Oct 20, 2005 11:13 am Reply with quote

That sounds fascinating Ciggywink - I'll add that to my Amazon wish list!

29168.  Tue Nov 01, 2005 7:28 am Reply with quote

Sorry to dredge this up, but I have a small point having read a book called "Why Elephants have big ears" by Chris Lavers.

Quite a good read (in parts), some good bits about Komodo Dragons and stuff which I will post elsewhere when time permits.

Anyway Flash Wrote:

we do stick by the assertion that all indigenous mammals in Australia are marsupials. To start you off: the dingo isn't indigenous, and neither is the rabbit.

Take us on, though, if you're hard enough.

You are fogetting the bats; there are plenty of species of bat indigenous to Oz. I can't find anything amazing to prove this on the web, but if you're in any doubt just type in bat, indigenous and australia into google.

29189.  Tue Nov 01, 2005 9:16 am Reply with quote

Well, unless they're marsupial bats I've completely repented of this assertion.

29190.  Tue Nov 01, 2005 9:21 am Reply with quote

... although I've now tracked it down - to Gray (post 21102), although I seem to have egged him on in the first place.

29255.  Tue Nov 01, 2005 5:34 pm Reply with quote

I can't find any references for indigenous Australian bats. They would surely never count anyway, as they could easily have flown to Australia any time in the last 60m years or so. I suppose it depends when 'indiginousness' starts.

This I found interesting, though:
A heated debate was recently triggered by the discovery that flying foxes, primates, and flying lemurs share a unique brain organization. (Flying lemurs, apparently close relatives of the true lemurs of Madagascar, are a poorly known group of cat-size gliding mammals that live in the Indonesian region and, like bats, are in a separate group of their own, the Dermoptera.) Did both the Micro- and Megachiroptera come from a single, shrew-like, gliding ancestor, or did the flying foxes evolve separately from primates?

If the latter notion is correct, are their unique brain characteristics sufficient reason for reclassifying flying lemurs and flying foxes as primates? The issue remains unresolved, but most scientists agree that bats are far more closely related to primates than to the rodents with which they often are linked in the public mind.

This site is not much more help about indigeniality:
There are 966 species of bat in the world, and 90 of those are found in Australia. They come in all sizes, from a tiny Malaysian bat the size of a bumble-bee, to a huge bat from New Guinea with a wing span of almost 2 metres (6').

At last - this seems to clinch it:
The earliest bat fossils in Australia come from Riversleigh, World Heritage Area, North Queensland and date to 25 million years (Early Miocene). The fossil record of Riversleigh’s bats is particularly extensive and has revealed much about the early bats that inhabited Australia. Naracoorte Cave’s fossil record of bats only includes two species, Miniopterus bassanii and Nyctophyllis geoffroyi.

Doesn't mean they evolved there, of course, so everything hinges on a proper definition of 'indigenous'.

29263.  Tue Nov 01, 2005 7:41 pm Reply with quote

Chris, on the business about Megachiroptera being primates, we noodled with the topic some time ago, and apparently it's an idea that was debated for a while but then knocked on the head. BobTheScientist's assertion that
the monophyly of bats is "done and dusted"

stuck in my mind for some reason; it's at post 4646 in the B Series 'Bats' thread.

29271.  Wed Nov 02, 2005 4:59 am Reply with quote

"done and dusted"
seems a little optimistic. A quarter of the mammal species on Earth are bats, and I should think a couple of percent of those have been subjected to molecular phylogeny analysis.

'Closeness' in genetic terms is a matter of deciding how long ago various branches split off from other branches, and bat skeletons are so thin that hardly ever fossilise, so it's DNA testing or nothing.

They're all bats, fairly clearly, but the debate as to whether some are 'closer' to primates than others will carry on for ever. It's all about interpretation - that is, how biologists force a linear measurement on something that is distinctly non-linear.

29276.  Wed Nov 02, 2005 6:09 am Reply with quote

I dare say you're right. I know nothing about this, although Bob is a specialist. You'll have seen the extract from the research paper he cited:
We use information on evolutionary rate differences for different types of sequence change to establish phylogenetic character weights, and we consider alternative rRNA alignment strategies in finding that this mtDNA data set clearly supports bat monophyly. This result is found despite variations in outgroup used, gap coding scheme, and order of input for DNA sequences in multiple alignment bouts. These findings are congruent with morphological characters including details of wing structure as well as cladistic analyses of amino acid sequences for three globin genes and indicate that neurological similarities between megabats and primates are due to either retention of primitive characters or to convergent evolution rather than to inheritance from a common ancestor.

Src: Phylogenetic relationships among megabats, microbats, and primates. Proc Natl Acad Sci U S A. 1991 Nov 15; 88(22): 10322-6.

29278.  Wed Nov 02, 2005 7:21 am Reply with quote

I don’t know whether I should really be letting this one lie, but I have gone from agreeing with the assertion 100%, to disagreeing 100%, to being not sure. I have just checked a few more sites, and I thought this may be worth posting.

Gray’s link claimed this:
The earliest bat fossils in Australia come from Riversleigh, World Heritage Area, North Queensland and date to 25 million years

However, it seems to be a little outdated. According to these two sites (from the Australian Government and Australian Museum) there have been developments.

There has been another big fossil-find since the Riversleigh one; this time in Murgon, Queensland. Apparently this find showed that at one stage placental mammals competed with Marsupials:

Five years ago the science magazine, Nature, reported that the tooth of a placental condylarth had been found in Australia. The presence of the placental condylarth in Australia suggests that marsupials and placentals were in Australia at the same time and that in the battle for supremacy, the marsupials won.

However, this is an aside. On the bat front: the oldest bat fossil, not just in Oz, but in the whole Southern Hemisphere has been found. Dating from 55 million years ago.

Until fossils of the Murgon Bat were found, scientists thought that bats first colonised Australia about 35 million years ago. Discovery of the Murgon Bat showed that bats have been on the continent for at least 55 million years.

You would think that the fact that no older fossil has been found within 5000 miles should prove indigenousness beyond question. However, something in me is not convinced. Maybe they’ve just not looked hard enough.

30079.  Tue Nov 08, 2005 12:38 am Reply with quote

Today, one of my cats met what appeared to be her first aggressive marsupial, judging by the surprise she showed when a hissing, drooling mouth opened to show some fifty teeth. An adult opossum was investigating the groundhog holes in my wood, with a view to finding a snug place to spend the winter. It was certainly a male, from the size, and probably did not realize that it was seriously overmatched against this small female cat. Fortunately, I was able to intervene before possum became the plat du jour.


Page 2 of 2
Goto page Previous  1, 2

All times are GMT - 5 Hours

Display posts from previous:   

Search Search Forums

Powered by phpBB © 2001, 2002 phpBB Group