New fossil reveals earliest ancestor for humans

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Hi arabianights:

Unfortunately I do not not have any convenient access to Nature.

If you have read the article you cited, perhaps you can explain its rationale for deciding the particular creature the article is about is an ancestor of humans. As I understand it, at any given time in the Earth's history when considering a particular kind of creature there would be many similar creatures coexisting. Therefore it seems plausible that anyone of many similar species all alive at that particular time might have been the one to have become humanity's ancestor.

Regards,
Buzz
 
Buzz Bloom said:
is an ancestor of humans.
I dunno, sounds like they looked a lot like us...
The bag-like body bears a prominent mouth and associated folds, and behind them up to four conical openings on either side of the body as well as possible sensory structures. An anus may have been absent, and correspondingly the lateral openings probably served to expel water and waste material. This new form has similarities to both the vetulicolianshttp://www.nature.com/nature/journal/vaop/ncurrent/full/nature21072.html#ref4 and vetulocystidshttp://www.nature.com/nature/journal/vaop/ncurrent/full/nature21072.html#ref5 and collectively these findings suggest that a key step in deuterostome evolution was the development of lateral openings that subsequently were co-opted as pharyngeal gillshttp://www.nature.com/nature/journal/vaop/ncurrent/full/nature21072.html#ref2, http://www.nature.com/nature/journal/vaop/ncurrent/full/nature21072.html#ref3, http://www.nature.com/nature/journal/vaop/ncurrent/full/nature21072.html#ref4, http://www.nature.com/nature/journal/vaop/ncurrent/full/nature21072.html#ref8.
 
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Interesting, but I am not sure what to make of it.

Among metazoans (multicellular animals, does not include plants or fungi which can also be multicellular) the deepest divide (evolutionarially speaking) is between protosotomes (arthropods, molluscs and many other invertebrates) and deuterostomes (various animals mentioned by the articles). This division is based upon the way their embryonic development goes through gastrulation (which some (embryologists) have called the most important stage of your life). Embryonic development generates the adult form of the animal.

Invagination during embryogenesis is important for generating mesoderm (the third embryonic cell layer) and the anterior-posterior body axis.
The difference between deuterostomes and protostomes lies in which end of the embryo invagination (different link) occurs.
In protostomes the invagination point becomes the mouth. In deuterostomes it is located where the anus would be.

The articles say the new fossil has a mouth but no anus, but is a deuterostome. Its possible it didn't form or closed up, but it is curious.
 
Hi arabianights:
Thanks for the reference. The following quote from the CNN article seems to logically include the point I was raising in post #2.
Biologically, Saccorhytus belongs to a broad category of creatures called deuterostomes. Half a billion years ago, they began to rapidly evolve into diverse branches, including vertebrates such as humans as well as sea squirts, starfish, sea urchins and acorn worms.​
The following is from Wikipedia.
Saccorhytus (from Latin saccus "bag" and Ancient Greek ῥύτις rhytis "wrinkle") is an extinct genus of animal belonging to the superphylum Deuterostomia,​

This seems to be saying (1) Saccorhytus is one of the species belonging to the superphylum Deuterostomes, and (2) some member of this super-phylum was the ancestor of all the vertebrates, which includes humans. However, there is nothing so far that explains why this particular species is the one that led to vertebrates and humans.

Regards,
Buzz