The Incredible Human Journey Read Free Page A

repeated glaciations and ending with the last ice age. As ice sheets grew and then
shrank back, sea levels would fall and rise. With differences of up to 60 million km 3 in the amount of water locked up as
ice, sea levels fluctuated by up to 140m. 7 The oxygen isotopes trapped in deep-sea cores and speleothem can be used to draw up a series of alternating cold and warm
stages called ‘oxygen isotope stages’, often abbreviated to OIS. Just looking at the last 200,000 years, there have been three
major cold periods (corresponding with oxygen isotope stages or OIS 2, 4 and 6) interspersed with four warmer periods (OIS
1, 3, 5 and 7). But the Pleistocene really was one long, cold ice age.
Interglacials account for less than 10 per cent of the time. 7
    At the moment we’re enjoying a nice, warm interglacial, oxygen isotope stage 1. The last full-glacial period, OIS 2, lasted
from 13,000 to 24,000 years ago. The peak of this most recent cold phase, around 18,000 to 19,000 years ago, is known as the
‘Last Glacial Maximum’ (or ‘LGM’).
OIS 3, from 24,000 to 59,000 years ago, was a bit warmer and more temperate, though still much colder than the present, and
is called an ‘interstadial’. OIS 4, from 59,000 to 74,000 years ago, was another full-glacial period, though nowhere near
as cold as OIS 2. 4 , 8 OIS 5, the last (sometimes called the ‘Eemian’ or ‘Ipswichian’) interglacial, was a warm, balmy period,
lasting from about 130,000 to 74,000 years ago. Before that, there was another glacial period, OIS 6, starting at about 190,000
years after the preceding interglacial, OIS 7.
    This level of detail might seem a bit excessive, but our ancient ancestors were very much at the mercy of the climate (as
we still are today). For instance, there was a population expansion during the wet warmth of OIS 5, and a crash, or ‘bottleneck’,
during the cold dryness of OIS 4. And sea levels fluctuated according to how much water was locked up in ice: during cold,
dry periods, sea levels were significantly lower – by as much as 100m – than during warm, wet periods. Between 13,000 and
74,000 years ago (i.e. during OIS 2–4), the world was a drier, colder place than it is today. Although the map of the world
was generally very similar, there was more land exposed; many of today’s islands would have been joined to the mainland, and
in places where the coast slopes gently the shoreline would have been much further out than it is today. This is of particular significance to archaeologists looking for traces of our ancestors along those ancient coasts – which
are now submerged.
    Stone Age Cultures
    Archaeologists classify periods differently from geologists, depending on what humans were doing at the time. During the Stone
Age, humans (including Homo sapiens and their ancestors) were making stone tools.
This is before metals – copper, tin, iron – were discovered and used. In fact, in the scheme of things, metal-working is a
very recent invention.
    The Stone Age is traditionally divided up into the Palaeolithic (old stone age – roughly corresponding with the Pleistocene period), Mesolithic (middle stone age) and Neolithic (new stone age). These stages happened at different times in different places, so it can become quite confusing.
The categories are also based on European prehistory, where much early archaeological work was carried out. But in terms of global archaeology, western Europe is a bit of a backwater, even a cul-de-sac 9 and so the terminology that has grown up there is sometimes rather unhelpful when we’re trying to understand what was happening
in the rest of the world. However, the categories at least provide us with a vocabulary and some kind of framework to help us think about the deep past.

    Table showing the relationship between geological periods, oxygen isotope stages and what humans were getting up to at the time.
    Each stage is characterised by different styles and ways of making stone tools,