'No large group is known to have maintained complete reproductive isolation for extended periods…
no matter the languages we speak or the colour of our skin, we share ancestors who planted rice on the banks of the Yangtze,
who first domesticated horses on the steppes of the Ukraine, who hunted giant sloths in the forests of North and South America, and
who laboured to build the Great Pyramid of Khufu.'
—Douglas Rohde, Steve Olsen & Joseph Chang, Modelling the recent common ancestry of all living humans,
in Nature (2004)
Population of the world and continental regions,
middle-aged adults (35-69 years): 1950-2010
Notes: Of the world's 2.19 billion middle-aged adults in 2005, 1.33 billion lived in Asia, 330 million in Europe,
200 million in Africa, 180 million in Latin America and the Caribbean, 130 million in Northern America, and more than 10 million in
Oceania.
The number of middle-aged adults passed 1 billion in 1968, then 2 billion in 2002. In the mid-2000s, the world's
middle-aged population was expanding by 48 million a year, of which 35 million a year was in
Asia (compared with 5 million a year in Africa, 4 million a year in Latin America and the Caribbean,
and 2 million a year each in Northern America and Europe).
Notes: Of the world's 2.19 billion middle-aged adults in 2005, 1.33 billion lived in Asia, 330 million in Europe, 200 million in Africa, 180 million in Latin America and the Caribbean, 130 million in Northern America, and more than 10 million in Oceania.
The number of middle-aged adults passed 1 billion in 1968, then 2 billion in 2002. In the mid-2000s, the world's middle-aged population was expanding by 48 million a year, of which 35 million a year was in Asia (compared with 5 million a year in Africa, 4 million a year in Latin America and the Caribbean, and 2 million a year each in Northern America and Europe).
Source of data: United Nations Population Division, "World Population Prospects: The 2006 Revision".