A. sediba, and The Star That Should Not Exist

A. sediba

The hominid Australopithecus sediba has been in the news again. A. sediba is considered to be at least close to the ancestral line of modern humans, and a recent study on a “nearly complete wrist and hand” strengthens this claim, in that it shows that the fossil has a mixture of hominid and Australopithecine features. Brian Thomas, always the contrarian, thinks otherwise.

When presented with examples of human ancestors Young Earth Creationists place them in one of two camps: Either the specimen is fully human – like Homo sapiens neanderthalensis and the Laetoli footprints likely caused by Australopithecus afarensis – or it is considered to be entirely ‘ape’. For the Creationists there is no middle ground.

Hence, Fossil Hand Points Away from Human Evolution. Brian Thomas begins:

In 2010, a new candidate was announced for humanity’s evolutionary tree—Australopithecus sediba. Now, recent analyses of its fossilised bones are being reported as further proof of its ancestral standing.

However, headlines presenting it as another rung on the human evolutionary ladder—such as “2-million-year-old fossils raise hope over ‘missing link,'” “Fossil Trove Sheds Light On a Stage of Evolution,” and “Rethinking Human Origins: Fossils Reveal a New Ancestor on the Family Tree”—all fly in the face of the actual data found in the five detailed reports describing it in the journal Science.

I agree completely that people who use the phrase ‘missing link’ – and headline writers in general – should be shot. But those headlines are little worse than his…

One of the scientific reports examined the features of each bone in the wrist and hand from what appears to have been an adult female. The unique hand doesn’t look like a modern ape’s, a modern human’s, or even some sort of gradual transition between the two. The researchers described it as a “mosaic” of features.

Ok, it’s in the middle, at least on average. Some things are at the stage that humans are at, some aren’t. As the abstract says:

The hand presents a suite of Australopithecus-like features, such as a strong flexor apparatus associated with arboreal locomotion, and Homo-like features, such as a long thumb and short fingers associated with precision gripping and possibly stone tool production.

Calling this not gradual is merely nit-picking. It can make tools, but it can also swing in trees. There is no reason why the evolution of humans couldn’t have gone through such a stage.

“Sediba’s” finger bones were long, curved, and—”together with its primitive australopith-like upper limb”—demonstrate that this small primate was fit for swinging through trees, unlike ground-dwelling humans.

Also, Sediba’s thumb was long and skinny. The human thumb is shorter in proportion to the fingers so that it can be used to build things and handle “large loads during stone tool production.” So Sediba’s thumb probably “was not subject to the same type or frequency of loading as that of other contemporary or later hominins.” Thus, this creature’s anatomy shows strong evidence that it did swing from tree branches and, despite reports to the contrary, did not make tools.

Why couldn’t it have done both? The thumb is still shorter than the fingers, by the way. Skipping ahead:

So, if Science says that this fossil adds “ambiguity,” how can the mainstream media say it “sheds light” on human evolution? Clearly, the scientific details do not match the headlines. But when it comes to human evolution, headlines typically don’t match reality.

Again, ‘human evolution’ is hardly alone on that count. The ‘ambiguity’ quote is related to the idea that we don’t quite know what the “functional significance” of the various hand types that have been found – this “adds to the…ambiguity” by providing more evidence to the situation. This is how it “sheds light” and this is how science works.

Reports in 2010 on Australopithecus sediba fossils made similar claims regarding the possibility that the species represents some human ancestor. But it, too, was quickly seen as “not a missing link.”

Again, if a scientist calls something a missing link that’s a bit of a red flag that they’re talking up their find. If they brush journalistic attempts for them to call a fossil such aside then this is all to the good.

The new Sediba hand fossils, from the same site as those described in 2010, clearly confirm what was concluded [by Mr Thomas here] last year. Rather than showing any transitional features between ape and man, the hand contains a mosaic of well-matched features that were uniquely fitted together—as though they belonged to a specially created, distinct creature.

I would very much like it if Mr Thomas took this to heart, and realised that no ‘transitional species’, any ‘missing link’, is going to be intrinsically any different from any other species that, due to pure chance, was discovered beforehand and so forms the edges of the gaps that must be bridged. That’s kind of the point, really. I would like it if the whole world realised this. But I doubt I’ll get my wish…

The Star That Should Not Exist

The moral of this story is that, if you make a prediction, you should always publicly record it before the fact. In short the other day I was directed – via the wonders of twitter – to a Astrobites post called A Star That Should Not Exist. This will be a DpSU, I said to myself. But I really should have posted that somewhere….

There are many ways to divide the stars in the sky into groups. One of the ways is by their metallicity. Basically, newer stars such as the sun have a higher metal* content, as there has been more time for heavier elements to be formed. They are referred to as Population I stars. Pop II stars have a lower metallicity and are older.

What has been found is a small dwarf star – SDSS J102915+172927, in Leo – that has such a low metal content that it is classed as a Population III star, a group that was previously considered to be a) much older, b) much bigger and c) to have burned out a long time ago. As wikipedia says:

[C]urrent stellar models show that Population III stars would have soon exhausted their fuel and exploded in extremely energetic pair-instability supernovae. Those explosions would have thoroughly dispersed their material, ejecting metals throughout the universe to be incorporated into the later generations of stars that are observed today.

This is indeed a puzzle. I would guess that an already anomalous in some way Pop III star managed to lose much of its mass without going nova. It has then hung on to life as a dwarf star for a few aeons ’til now. Someday we will learn the real answer, but while I’m guessing that it may turn up in Astrobites it probably wont be a DpSU.

As I said, Brian Thomas wrote a DpSU on this, called Lightweight Star Should Not Exist. He touches on the doubt surrounding the ability of stars to form in the first place, quoting a study author as saying:

A widely accepted theory predicts that stars like this, with low mass and extremely low quantities of metals, shouldn’t exist because the clouds of material from which they formed could never have condensed.

However the next statement was left out:

[W]e may have to revisit some of the star formation models.

In short: we don’t know everything, and science marches on. Because we don’t know something now doesn’t mean we never will. Science, unlike the ICR, is not certain. We don’t know, but we will know.

Amusingly, B.T. says at the start that “according to the Bible’s account of star formation, however, the existence of such a star is no puzzle at all.” The bible’s account, you understand, is ‘God made them.’ God can do anything , theoretically- this explains everything and also nothing. How did god make them?

*That is to say, elements that are not hydrogen or helium.

2 thoughts on “A. sediba, and The Star That Should Not Exist

  1. “This will be a DpSU, I said to myself. But I really should have posted that somewhere…”

    Been there, not done that. In the meantime, I’ve tried to post pre-rebuttals, but they never materialized in creationist accounts. 😦

  2. Pingback: A. sediba and the Laetoli Footprints « Eye on the ICR


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