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Map of early human migrations based on the Out of Africa theory; figures are in thousands of years ago (kya). [1]The peopling of the Americas began when Paleolithic hunter-gatherers (Paleo-Indians) entered North America from the North Asian Mammoth steppe via the Beringia land bridge, which had formed between northeastern Siberia and western Alaska due to the lowering of sea level during the ...
Robert Neil Butler (January 21, 1927 – July 4, 2010) was an American physician, gerontologist, psychiatrist, and author, who was the first director of the National Institute on Aging. Butler is known for his work on the social needs and the rights of the elderly and for his research on healthy aging and the dementias.
Shanas graduated in 1949 at the University of Chicago with a dissertation on the social aspects of aging, under the mentorship of Ernest Burgess and Robert J. Havighurst. [3] She worked at the University of Chicago until 1965, as a member of the university’s Committee on Human Development, a lecturer in Sociology and a staff member of the ...
Examples of Clovis and other Paleoindian point forms, markers of archaeological cultures in North America. The Solutrean hypothesis on the peopling of the Americas is the claim that the earliest human migration to the Americas began from Europe during the Solutrean Period, with Europeans traveling along pack ice in the Atlantic Ocean.
Schematic illustration of maternal (mtDNA) gene-flow in and out of Beringia, from 25,000 years ago to present. The genetic history of the Indigenous peoples of the Americas is divided into two distinct periods: the initial peopling of the Americas from about 20,000 to 14,000 years ago (20–14 kya), and European contact, after about 500 years ago.
By 2030, 20% of Americans are predicted to be past the age of retirement, which could pose a burden to the healthcare system. Older and retired people tend to need more health services, which must be provided by their younger counterparts, so some demographers have theorized that this could have a negative impact on the country. [46]
In 1968 it took the form and became known as the neuroendocrine theory of aging. [38] [39] [40] 1956 Denham Harman proposed the free-radical theory of aging and demonstrated that free radical reactions contribute to the degradation of biological systems. [41] The theory is based on the ideas of Rebeca Gerschman and her colleagues put forward in ...
Older people have different requirements from society and government, and frequently have differing values as well, such as for property and pension rights. [1] Older people are also more likely to vote, and in many countries the young are forbidden from voting. Thus, the aged have comparatively more, or at least different, political influence. [2]