life history
edyong | February 22, 2010An assortment of tree-living mammals
In The Descent of Man, Darwin talked about the benefits of life among the treetops, citing the "power of quickly climbing trees, so as to escape from enemies". Around 140 years later, these benefits have been confirmed by Milena Shattuck and Scott Williams from the University of Illinois.
By looking at 776 species of mammals, they have found that on average, tree-dwellers live longer than their similarly sized land-lubbing counterparts. Animals that spend only part of their time in trees have lifespans that either lie somewhere between the two extremes or…
edyong | March 28, 2009
Animals have distinct personalities and temperaments, but why would evolution favour these over more flexible and adaptible mindsets? New game theory models show that animal personalities are a natural progression from the choices they make over how to live and reproduce.
Any pet owner, wildlife photographer or zookeeper will tell you that animals have distinct personalities. Some are aggressive, others are docile; some are bold, others are timid.
In some circles, ascribing personalities to animals is still a cardinal sin of biology and warrants being branded with a scarlet A (for…
edyong | October 11, 2008
While philosophers and poets muse on the meaning of life, natural selection casts a dispassionate eye on the whole affair. From the viewpoint of evolution, there is only one thing that matters - that we survive long enough to pass our genes on to the next generation, as many times as possible. And from the viewpoint of evolution, we are not doing a very good job.
Birth rates in several countries around the world - the UK, Japan, China - are falling dramatically. Women are having fewer children and they are having them later, close to the end of their fertile period. But the fact that…
edyong | August 18, 2008People in most parts of the world are living longer and longer, thanks to great leaps in medicine and sanitation over the last century. But these growing life expectancies bring with them a sense of unease. The biggest worry is the possibility that medical advances are artificially prolonging life with little regard for its quality. Old age, after all, brings with it an increased risk of chronic diseases such as cancer, as well as both physical and mental decline.
This is not just a moral question, but an economic one too. The "oldest-old" are the fastest growing demographic in Western…
edyong | August 6, 2008A good defence was a vital part of life in the Cretaceous. Plant-eaters needed effective ways of warding off the crushing jaws of Tyrannosaurus and its kin. Some species like Triceratops and Ankylosaurus had fairly obvious protective equipment, including horns, frills and armoured plates. But others lacked defensive armaments, and had to fend off predators through subtler means.
Take Hypacrosaurus. It was one of the duck-billed dinosaurs known as hadrosaurs, and like most other members of the group, its soft body lacked any obvious protection. Its main advantage was size; a fully-grown adult…
edyong | July 14, 2008Evolution dances to the tune of death. Killers - be they predators, diseases or competitive peers - can radically shape a species' life cycles by striking down individuals of a certain age. The survivors respond by changing their "life histories" - a collection of traits that defines their reproductive cycles, including how often they breed, when they start to do so and how many young they have.
If an animal's adult life is short and brutal, they tend to grow quickly and become sexually mature at a young age - a strategy that maximises their chances of siring the next generation. The…
edyong | April 1, 2008You could argue that life is all about cheating death and having enough sex to pass on your genes to the next generation, as many times as possible. From this dispassionate viewpoint, human reproduction is very perplexing for our reproductive potential has an early expiry date. At an average age of 38, women start becoming rapidly less fertile only to permanently lose the ability to have children some 10 years later during menopause.
From an evolutionary point of view, this decline is bizarre. Other long-lived animals stay fertile until close to the end of their lives, with elephants…