Anthropology.net

Hat tip to Luis, who pointed me towards a website by the name of Las Piedras, on which there are numerous images of stones recovered from fields in southern Spain – although there is no accompanying text, the word is that the author of the site collected a large number of pebbles whilst out field-walking. Her finds exhibit what at first appears to be some sort of mineral inclusion, as all the rocks, which are light in colour, are marked by lines and shapes which in many cases, appear as if they could have been made by human hand, but look as if they could be natural.

There is a distinct linearity in many of the pebbles – wavy lines, straight lines and crosses, for example, whilst still others hint vaguely at what might be human or animal shapes, even a boat, rather in the style of North African rock art panels, or the Iberian Neolithic, whilst yet still others bear shapes which hint at some sort of ancient alphabetic or numeric script.

But rather than dwell on what they might or might not be, I prefer to leave it to readers to decide for themselves – my knowledge of geology is scant, and mineralogy even less, and it may well be the case that someone out there will have an immediate explanation that points to a natural origin for these dark markings. Alternatively someone might have seen a similar type of rock art from elsewhere in the world and offer a clue that might confirm their artificiality – obviously it’s difficult to make any conclusive decision with only images on a web page to make a call, but as far as I understand it, the author has spoken to various people she considered capable of offering further clues, but has thus far come up blank – one opinion was that the markings were caused by ploughing, but that seems unlikely to me.

The site is divided into various sections, with one gallery, Las Piedras giving a glimpse of some of the stones and the context in which they were found, whilst the second, Los Lugares gives a map of the general area, with highlighted areas which link to images of stones found in those places.

The final section, Los Signos, takes us through a series of images where many of the stones appear to have designs or abstract figures, amongst which are to be found some of the more compelling markings – although as I mentioned earlier, I have no real way of confirming artefactual authenticity, any idea of how old such humanly modified rocks might be, or indeed whether they just appear to be artificial to eyes that automatically make graphic assumptions based on past visual experience.

The author professes to be just as puzzled by these stones as myself and Luis, and I’m told she has posted the images online with the express purpose of discovering more about them via an online response from someone out there who might know one way or the other. At the very least, there are many fascinating images that might just spark the curiosity, so feel free to head on over and check them out.

This looks like a pretty interesting paper, postulating that mtDNA diversity is lower in populations residing in cooler climates – it’s free to access here, and in the meantime, here’s the abstract:

There is an ongoing discussion in the literature on whether human mitochondrial DNA (mtDNA) evolves neutrally. There have been previous claims for natural selection on human mtDNA based on an excess of non-synonymous mutations and higher evolutionary persistence of specific mitochondrial mutations in Arctic populations. However, these findings were not supported by the reanalysis of larger datasets.

Using a geographical framework, we perform the first direct test of the relative extent to which climate and past demography have shaped the current spatial distribution of mtDNA sequences worldwide. We show that populations living in colder environments have lower mitochondrial diversity and that the genetic differentiation between pairs of populations correlates with difference in temperature.

These associations were unique to mtDNA; we could not find a similar pattern in any other genetic marker. We were able to identify two correlated non-synonymous point mutations in the ND3 and ATP6 genes characterized by a clear association with temperature, which appear to be plausible targets of natural selection producing the association with climate. The same mutations have been previously shown to be associated with variation in mitochondrial pH and calcium dynamics. Our results indicate that natural selection mediated by climate has contributed to shape the current distribution of mtDNA.

posted via Yann Klimentidis’ Weblog.

Reference: Climate shaped the worldwide distribution of human mitochondrial DNA sequence variation François Balloux, Lori-Jayne Lawson Handley, Thibaut Jombart, Hua Liu and Andrea Manica.

Published online before print July 8, 2009, doi: 10.1098/rspb.2009.0752