SATURDAY, 6 AUGUST 2011Humans are unique among animals in developing neurodegenerative diseases such as Alzheimer’s. As we age, the human brain shrinks in volume, particularly in regions associated with learning and memory. Research published in PNAS found that while parts of the human brain can reduce in size by as much as a 25% by age 80, chimps show no significant age-related shrinkage at all .
Humans have larger brains and longer lifespans than other primates. These traits evolved because they provided a fitness advantage to humans– a larger brain allows more complex behaviour, and it has been suggested that having elderly grandparents around can assist in the care of offspring that take longer to reach maturity due to the time required for growth of their larger brains.
However, it appears that these traits may have come with a cost. Humans are uniquely vulnerable to dementing illnesses, and even healthy human ageing is associated with deterioration of the brain. It seems that our large, metabolically-expensive brains may amplify the effects of ageing and leave us vulnerable to age-related neurodegenerative diseases towards the ends of our lives .
Written by Catherine Moir