2019-04-20_New_Scientist

20 April 2019 | NewScientist | 53

“ It’s not just polar bears breeding with

grizzlies: humans also interbred with others”

p 29). In the UK, the people who
built Stonehenge probably left a
genetic legacy. Studies show an
influx of DNA from 2450 BC, after
which Yamnaya DNA varied from
60 to 100 per cent between
individuals. By 2100 BC, levels had
stabilised to about 5 to 15 per cent
Neolithic DNA, and this endured
into the Iron Age of 800 BC.
It isn’t possible to draw more
certain conclusions, since the
relative population sizes are
unknown. There is a gap in the
data for about 27 generations
from 3000 BC to 2450 BC, so we
cannot assume a sudden influx.
Neolithic pottery was very
similar to other “Beaker” styles.
As Barras notes, life was changing
before the steppe people arrived.
There is very little evidence of
conflict in Britain in 2500 BC.
The proposal that the newcomers
were mostly male is contested.
The effect seen in the DNA can be

explained by a large influx of

people arriving to meet a smaller

initial population.

From Erik Kroon,

Leiden, The Netherlands

I was most pleased to see my

field of study – Corded Ware

culture – featured on your cover.

But the mention of genocide and

“Stone Age conquerors” is, to my

mind, overstating the evidence.

Migration is no doubt a factor

in the changes observed in the

third millennium BC in Europe,

but that doesn’t equal genocide

or conquest. Genetic data indeed

show a major shift in ancestry for

the Beaker cultures; the data also

show a resurgence of indigenous

genetic material later.

We cannot interpret genetic

data without taking into account

biases related to geography,

selection of areas of historical

research foci and archaeological

Ask the goldilocks

planet: it doesn’t care

From Philip Bolt,

Kirriemuir, Angus, UK

I was interested to read about

evolution by persistence and its

connection to the Gaia hypothesis

of a self-regulating planet

(23 March, p 34). It got me thinking

about a crucial part of the theory.

Gaia doesn’t care.

There is a danger that some

people reading the article will take

comfort in the belief that Gaia will

“act” to ameliorate the effects of

global warming and return us to

a pre-industrial stable state.

This would miss the point that

our current problem has arisen

because whatever mechanisms

exist to maintain an equilibrium

have been overloaded.

It is possible, and perhaps it is

probable, that Gaia will undergo

a number of changes of state to

preservation. The interactions

between “indigenous” cultures

and Yamnaya migrants bear

further analysis.

From Robert Bright, Bedford, UK

Some questions sprang to mind

about the spread of the livestock

herders called the Yamnaya.

Where does this name come

from? Barras refers to some of

the Yamnaya travelling to the

Indian subcontinent. Is this

perhaps the origin of the Indo-

European family of languages?

The editor writes:

Q The name is from “Yamnaya

Kultura”, a transliteration of the

Russian for “pit culture” – named

in modern times after the form

of their “kurgan” graves. Many

researchers do believe that these

people spoke proto-Indo-

European and introduced it

to India (4 July 2015, p 28).

Alice Outwater could be more surprised at Homo sapiens

interbreeding relatively recently with Denisovans (6 April, p 9)

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