Comments on: Earliest Animals https://gregladen.com/blog/2009/02/09/earliest-animals/ Tue, 10 Feb 2009 12:49:17 +0000 hourly 1 https://wordpress.org/?v=6.4.8 By: Vasha https://gregladen.com/blog/2009/02/09/earliest-animals/#comment-530707 Tue, 10 Feb 2009 12:49:17 +0000 http://scienceblogs.com/gregladen/2009/02/09/earliest-animals/#comment-530707 Thanks Robert, but that article is behind the paywall. The headline does say that the find “places the rise of the sponge lineage more than 635 million years ago” — what reasons do they give for thinking that the molecule does belong to the sponge lineage? When were the Demospongiae previously thought to have separated from the other animals?

]]> By: Virgil Samms https://gregladen.com/blog/2009/02/09/earliest-animals/#comment-530706 Tue, 10 Feb 2009 08:51:57 +0000 http://scienceblogs.com/gregladen/2009/02/09/earliest-animals/#comment-530706

If true, it means Demospongiae arose in an extremely harsh environment, not the relatively warm seas of today.

Everyone knows that cold climates encourage industriousness and thrift.

]]> By: Robert Saunders https://gregladen.com/blog/2009/02/09/earliest-animals/#comment-530705 Tue, 10 Feb 2009 00:21:44 +0000 http://scienceblogs.com/gregladen/2009/02/09/earliest-animals/#comment-530705 Vasha – The “News and Views” article that accompanies the Nature paper (see http://tinyurl.com/bldepx) makes pretty much those points, and gives a more “biological” view of the finding.

Robert

]]> By: Vasha https://gregladen.com/blog/2009/02/09/earliest-animals/#comment-530704 Mon, 09 Feb 2009 21:59:07 +0000 http://scienceblogs.com/gregladen/2009/02/09/earliest-animals/#comment-530704 OK, I don’t get this. The article quotes “paleobiologist Kevin Peterson” as saying that this confirms that “we animals can all trace our origins back to sponges.” — although this is not in quotes so may be a misrepresentation. Now, if Demospongiae have 24-IPC and other animals don’t, they must either have developed it after the separation of lineages or it’s a plesiomorphy that all other animals have lost. The quote is obviously relying on the second alternative being true. But in that case, what indicates that these 635-million-year-old animals were “sponges”, let alone Demospongiae? For all we know, 24-IPC could have first arisen in single-celled organisms and subsequently been lost once or several times. We now know just one (molecular) character of these old organisms, which they happen to share with extant animals that are on a basal branch; it’s a big leap to assuming that they were similar in other ways.

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