Articles to 2019-03-07

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First the link to this week's complete list as HTML and as PDF.


Loftus et al. and Smith et al. offer new insights into the prevalence of shell mounds at the transition from the Middle to the Late Stone Age. It seems shellfish began not as a preferred but as a fallback food. Similar to wild grain the reliability of this fallback permitted a strong growth and high density of population, forcing them into making the former fallback their main staple.


Cech & Blair-Loy report on young parents leaving full-time STEM employment after the birth of their first child. The claims in their discussion are not actually wrong. Nearly twice as many (45 %) mothers leave as fathers do (25 %). Nevertheless these numbers are quite misleading. Women always leave STEM employments at a higher rate than men do. For both fathers and mothers the number of leavers is one and a half times that of childless employees of the same sex (supplementary figures S1 and S2), there is no sex difference in the effect of parenthood. Taking full- and part-time employment together, the share of parents staying within STEM is nearly the same for fathers (79 %) and mothers (69 %) and the difference vanishes when correcting for those leaving employment altogether (1 % vs. 13 %).

There also is a noticeable difference in timing. Except for those leaving employment altogether the change for mothers is instantaneous – probably not returning from maternal leave – while that for fathers is more drawn out with half of it occurring much later. This hints at different motives being at work here. A possible driver for fathers might be looking for higher pay around the time the child starts pre-school and kindergarden and parents have more social contact with parents from other areas and are socially less involved with work colleagues alone. The timing for fathers leaving STEM matches that for mothers leaving employment.

In sum parenthood does tend to drive young parents out of STEM but this effect is independent of sex – contrary to what the authors imply in their abstract and discussion.


I came across Deloison 2004 through personal contact with her German translator. She rightly stresses a few points, that were and are if not exactly new at least widely under-appreciated. Humans are not descended from the great apes, those are equally far distanced from the last common ancestor as we are with probably just as much change and development. I first read of the notion, that this ancestor lived in more open vegetation and covered more open ground and that the apes only withdrew into the forests later, in Desmond Morris' Naked Ape of 1967. That this ancestor never used knuckle walking is proved by the fact, that knuckle walking evolved independently in gorillas and chimpanzees and through slighty different anatomical pathways (Kivell 2009 in PNAS and Harcourt-Smith 2004 (list of 2013-11-22), both later than Deloison).

Deloison’s suggested family tree with its very early split between the human and the ape line is manifestly wrong, though. It's not her fault. Her book was published in 2004 and probably largely finished a year or two before that. The first human genome was published in 2003 and the ape ones, establishing the correct tree and estimates for the timing of splits, only later. The main publication for Ardipithecus ramidus, a possible candidate for a place near the split (but still about 2 Ma too late) came out in 2009 (Lovejoy in science).

In sum, what may have been a pioneering and innovative contribution in 2004 is not really worth reading today. This is not to denigrate the author but a fact of life in a fast moving discipline.


The literature on paleoclimate abounds with temperature curves looking exactly similar to the ice core isotopes they were generated from. This has always bothered me. Oxygen isotope ratios depend on total ice mass, sea surface temperature when evaporating, temperature and precipitation during transport, and the temperature when falling as snow, with all these effects possessing similar orders of magnitude. I had expected modelers at least to try correcting for known confounders. Reading Sime et al. confirms my suspicion that this seems rarely to be the case in practice. If so this has wide reaching consequences and throws many well accepted conclusions into doubt.


The renowned statistician McKitrick has done it again. Together with Christy they wrote a masterful introduction into what models are, what they can and can't achieve, and most importantly how to test their validity. As their example they demonstrate how infinitely tuneable climate models have been tuned towards their desired results and can be shown to fail for one of their strongest and most important subsidiary predictions.


Hodgson has managed to attempt a comprehensive review into the neural basis and genesis of art without a single mention of Lewis-Williams (1988, list of 2011-03-12 and three important monographs). While not detracting from the importance of his observations, this makes them much less novel than Hodgson seems to assume.

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