Thursday, July 12, 2018

The Braided River

The Waimakariri River in the South Island of New Zealand is braided over most of its course
By I, Gobeirne, CC BY 2.5,

If you look for an inheritance tree, you will find a tree; but a tree is only a model.
Multiregional theory of human origins in Africa:
The New Story of Humanity's Origins in Africa
Several new discoveries suggest that our species didn’t arise from a single point in space. Instead, the entire continent was our cradle.

Perhaps the same is true for the Indo-European languages.

Excerpt, emphasis added:

This can be a tricky concept to grasp, because we’re so used to thinking about ancestry in terms of trees, whether it’s a family tree that unites members of a clan or an evolutionary tree that charts the relationships between species. Trees have single trunks that splay out into neatly dividing branches. They shift our thoughts toward single origins. Even if humans were widespread throughout Africa 300,000 years ago, surely we must have started somewhere.

Not so, according to the African-multiregionalism advocates. They’re arguing that Homo sapiens emerged from an ancestral hominid that was itself widespread through Africa, and had already separated into lots of isolated populations. We evolved within these groups, which occasionally mated with each other, and perhaps with other contemporaneous hominids like Homo naledi.

The best metaphor for this isn’t a tree. It’s a braided river—a group of streams that are all part of the same system, but that weave into and out of each other.

These streams eventually merge into the same big channel, but it takes time—hundreds of thousands of years. For most of our history, any one group of Homo sapiens had just some of the full constellation of features that we use to define ourselves. “People back then looked more different to each other than any populations do today," says Scerri, “and it’s very hard to answer what an early Homo sapiens looked like. But there was then a continent-wide trend to the modern human form.” Indeed, the first people who had the complete set probably appeared between 40,000 and 100,000 years ago.

Wednesday, July 04, 2018

Sri Lanka: Agriculture in the Pleistocene?

Anil Suri has an article at How Old Is Indian Agriculture?

The article goes over some well-known findings; but also makes an extraordinary claim.

To trace the trajectory from incipient cultivation as a dry crop to the wetland crop rice had become by around 7500 BCE, we must journey south, indeed, as far down as the southern part of Sri Lanka. To the mesmerizingly beautiful Horton Plains National Park, to be precise. Here, there is evidence of cattle herding and grazing, microcharcoal indicating the use of fire to clear the land of forests, cultivation of edible plants, and early management of barley and oats from – hold your breath – 15,500 BCE. It is believed the subcontinent experienced a semi-arid climate between 22,000 and 15,500 BCE, followed by a sustained, progressively warmer spell, with a concomitantly strengthening monsoon, starting around 16,500 BCE. Thus, early attempts at pastoralism and agriculture begin almost as soon as the climate became ever so slightly conducive. The climate got progressively better for agriculture, peaking in an extremely humid period around 6700 BCE. As the humidity increased, cultivated rice made its first known appearance here around 13,000 BCE. Notice that the early dwellers of the Horton Plains seem to have figured out which crop was best suited to a particular climate. Closely following the improvement in the climate, intensive agriculture in the region began around 11,000 BCE, and there was an abrupt shift in emphasis from oats and barley to rice after 8000 BCE. The fact that intensive rice cultivation was being done on the Ganga plain by no later than the mid-8th millennium BCE, as described above, shows there were many independent centres for the establishment of agriculture in the subcontinent, and that the progress in agriculture happened closely in tandem with climactic changes.

In around 16,000 BCE, which falls in the Ice Age, India and Sri Lanka would have been contiguous as the sea level was about 120 metres lower than it is today. (Around 8000 BCE, it was still 50 metres lower.) This early attempt at agriculture was no flash in the pan. Archaeologists believe that there is a continuity of agricultural tradition in the subcontinent right from then. The archaeologist, Premathilake writes, The evidence of early form of agricultural activities found in the Horton Plains do not appear to have got isolated at the regional level and similar type of evidence in the form of cultivated pollen and other proxies is available in the Indian subcontinent.

Horton Plains is called "Maha Eliya Thanne" by the locals.

  1. The above claim is based on the 2006 paper by R. Premathilake, "The emergence of early agriculture in the Horton Plains, central Sri Lanka: linked to late Pleistocene and early Holocene climatic changes", which seems to have been pretty much ignored, if one goes by the number of citations this paper has received.  A quick search does not show any follow-up activity going on either.

  2. The Premathilake paper says: "It is clear that incipient management of barley and oats occur around 15 500 BC in the Horton Plains as evidenced by pollen and other multi-proxy records (e.g. phytoliths, diatoms, stable carbon isotope, organic carbon, total carbon, environmental mineral magnetic). The semi- humid event between 15 600 and 14 000 BC corresponds to incipient management of cereal plants (oats and barley). The pollen evidence also indicates herding, possibly of Bos sp. and supportive indications are (1) forest clearance/ burning, (2) grazing, (3) pastures, (4) the presence of a characteristic edible plant, (5) a cultivated shrub, (6) various types of disturbed fields, e.g: patanas, (7) enhanced anthropogenic erosion as indicated by the initial increase of the values in magnetic susceptibility parameters (8) and high percentages of microscopic charcoal particles. These observations can be interpreted as the result of the initial stage of slash- and-burn activity."
Agriculture 16000 years ago is an extraordinary claim and I think that these findings are in need of independent replication; and presumably much more intensive studies of the Maha Eliya Thanne region are called for.

Tuesday, July 03, 2018

On Denmark's Laws for Immigrant Ghettos

The NYTimes has a news-item  In Denmark, Harsh New Laws for Immigrant ‘Ghettos’.
Starting at the age of 1, “ghetto children” must be separated from their families for at least 25 hours a week, not including nap time, for mandatory instruction in “Danish values,” including the traditions of Christmas and Easter, and Danish language. Noncompliance could result in a stoppage of welfare payments. Other Danish citizens are free to choose whether to enroll children in preschool up to the age of six.

Sunday, July 01, 2018

Luck or method?

Manasataramgini has a problem from plane geometry embedded in a short story, which I extract here:
Given a unit square, if a point lies on the same plane as the square at not more than a unit distance simultaneously from each of the four vertices of the square then what will be: 1) the minimum distance it can reach from any side of the square; 2) what fraction of the area of the square can the point be located in.
Since the short story includes the requirement of solving it in 7 minutes, I was asked to try my hand at it.