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MUTATION ACCUMULATION. "Medawar reasoned that, if the effects of a deleterious mutation were restricted to late ages, when reproduction has largely stopped and future survival is unlikely, carriers of the negative mutation would have already passed it on to the next generation before the negative late-life effects would become apparent. In such a situation, natural selection would be weak and inefficient at eliminating such a mutation, and over evolutionary time such effectively neutral mutations would accumulate in the population by genetic drift, which in turn would lead to the evolution of aging.” http://www.nature.com/scitable/knowledge/library/the-evolution-of-aging-23651151 View in LinkedIn

SNUFFING MUTATIONS. “If a beneficial or deleterious mutation occurs only after reproduction has ceased, then it will not affect fitness (reproductive success) and can therefore not be efficiently selected for or against. However, even if a mutation occurs earlier, say during the reproductive period, its effects may not be visible to selection since, if extrinsic, environmentally imposed mortality is high, individuals that could express the mutation are likely to be dead already.” http://www.nature.com/scitable/knowledge/library/the-evolution-of-aging-23651151 View in LinkedIn

RURAL REASONS. “This decline is in line with that of many other farmland species and is attributed to changes in farming practices: the switch from spring- to autumn-sown cereals; increased use of pesticides; increased use of herbicides; the switch from haymaking to cutting for silage before the grass has set seed; reduced spillage of grain and improved; storage to meet EU regulations.” https://www.britishbirds.co.uk/wp-content/uploads/article_files/V96/V96_N09/V96_N09_P439_446_A004.pdf View in LinkedIn

EARLY DEMISE. “For most organisms, the natural world is dangerous since it abounds with competitors, predators, pathogens, accidents, and other hazards. It follows from this that in natural populations most individuals die or get killed before they can grow old and suffer the symptoms of aging: thus, individuals have a very small overall probability of being alive and reproductive at an advanced age.” http://www.nature.com/scitable/knowledge/library/the-evolution-of-aging-23651151 View in LinkedIn

COUNTRY SPARROW POPULATIONS. “The House Sparrow index from 1970 to 1999, shows an increase up to 1979 followed by a decline of about 60%, although this had flattened out by 1995, suggesting that the farmland population has now stabilised at a new, lower level.” https://lnkd.in/ezA77j7 View in LinkedIn

THE SELECTION SHADOW. "The key conceptual insight that allowed Medawar, Williams, and others, to develop the evolutionary theory of aging is based on the notion that the force of natural selection, a measure of how effectively selection acts on survival rate or fecundity as a function of age, declines with progressive age. As a consequence, selection is unable to favor beneficial effects, or to counteract deleterious effects, when these effects are expressed at advanced ages.” http://www.nature.com/scitable/knowledge/library/the-evolution-of-aging-23651151 View in LinkedIn

CENTRAL LONDON EXTINCTION. “While both urban and rural populations have undergone severe change, it is the decline in city centres which has attracted the most attention. Central London, along with the urban cores of Edinburgh and Glasgow, appears to be reporting near local extinction.” Nobody growing up in London does not recall the sheer abundance of sparrows in parks.” https://lnkd.in/eTu-5Ri View in LinkedIn

REPAIR SYSTEMS. “These results provide evidence that natural selection acts on species when longevity evolves, give insights into adaptive genetic changes associated with the evolution of longevity in mammals, and provide evidence that at least some repair systems are selected for when longevity increases.” https://lnkd.in/eFtw_Ub View in LinkedIn

URBAN SPARROWS. “The situation with sparrows in built-up areas is much more complex, with a gradual decline until about 1990. Since then, a massive decrease has led to almost complete extinction in some urban centres, while in the suburbs and small rural towns, sparrows have decreased little, if at all.” https://lnkd.in/ezA77j7 View in LinkedIn

HALDANE, MEDAWAR, AND WILLIAMS argued, “aging evolves because natural selection becomes inefficient at maintaining function (and fitness) at old age. Their ideas were later mathematically formalized by William D. Hamilton and Brian Charlesworth in the 1960's and 1970's, and today they are empirically well supported.” http://www.nature.com/scitable/knowledge/library/the-evolution-of-aging-23651151 View in LinkedIn