Animals use smell to sniff out predators, and to hide from them.
For humans, vision is the dominant sense, and we often overlook the importance of odour (although we’re reminded on those occasions we find ourselves sat next to someone who’s never discovered deodorant, or driving past a particularly pungent farm). But for most animals, it’s all about smell. Two new studies published last month highlight the importance of smell in the lives of animals as different as flies and snakes.
The brilliant mathematician and biologist JBS Haldane is famously quoted as once having said, “God had an inordinate fondness for beetles”. He was referring to the fact that nearly half of all insect species known are beetles, but over 50 years after his death, scientists are still gaining new insights into their amazing success. A new study reconstructing the beetle family tree suggests that it is the versatility of beetles that has allowed them to survive even the most testing of times.
One scientist found his laboratory stink bugs were laying different colour eggs on the black and white squares of a crossword printed on the newspaper lining of their cage. This small observation led him to begin a series of experiments that show how female stink bugs are able to selectively provide sun protection for vulnerable eggs.
Natural selection is incredibly good at adapting organisms to their environment, even those environments that are harsh and difficult to live in. But the changes currently happening to the World’s climate, hydrology and land-use may be too rapid for natural selection to act, in most cases. For some species, natural selection has provided the tools to adapt more rapidly, through behavioural or physiological changes. A few species have gone further still, evolving the ability to edit their own genes as they are expressed. Recent research shows this ability is used rampantly by certain species of squid, which may explain why they have responded relatively well to human impacts on the environment so far.
Sloths might be notorious for their leisurely pace of life, but research published last year shows they are no slow coaches when it comes to evolution.
Sloths, as we know and love them, are small, slow-moving creatures found in the trees of tropical rainforests. But modern sloths are pretty odd compared to their extinct relatives. Sloths (Folivora) are represented today by just six species in two families; the Megalonychidae (two-toed sloths) and the Bradypodidae (three-toed sloths). But 20,000 years ago there were perhaps as many as 50 species of sloth spread across the globe, and most were relatively large, ground-dwelling animals quite unlike modern sloths. While most modern sloths weigh in at a modest 6kg, extinct species such as Megatherium americanum and Eremotherium eomigrans could weigh up to 5 tonnes!
Not the most pervasive of suburban legends, granted, but it seems to keep popping up. It goes something like this…
Confused Farmer finds Hen is now Cock
The mature hen, Gertie, who had laid eggs the previous year, suddenly stopped, grew chin wattles and started to crow.
So, can chickens really change sex?
The short answer – No.
The field of research into personality and behavioural syndromes in animals has blossomed over the past few decades. With ample evidence for it’s existence, biologists have begun to consider its evolution; what is the adaptive benefit of personality? How are multiple personality types maintained in a population? Why do personalities exist when they sometimes result in maladaptive responses?
All these questions, and any evolutionary questions we might care to ask, make the assumption that personality is heritable. Without heritability, personality cannot be passed from generation to generation, and cannot be subject to natural selection. There is now plenty of evidence for high heritability of many personality traits in animals, although there is also an important influence of the environment too. Heritabilities estimates vary, from 0.22 – 0.61 in wild great tits, 0.32 in social spiders, 0.54 – 0.66 in humans and 0.2 – 0.8 in dumpling squid. These genetic influences may in part be reflected in brain morphology; one study in humans found differences in brain structure relating to neuroticism, conscientiousness, and extraversion. More neurotic people have a smaller total brain volume and a smaller frontotemporal surface area, whilst extraverts have a thinner inferior frontal gyrus.
When we look at other primates, although the similarities are clear, there are also several stark contrasts. Most noticeable, is our gait – humans are the only truly bipedal (upright walking) primates. Bipedality appeared early in human evolution, and may have marked our divergence from Chimpanzees around 6 million years ago. Bipedality had a number of benefits, allowing us to adapt to a new habitat, and freeing up our hands for other tasks, but compromises also had to be made. Changes in the shape of our pelvis, which enabled us to walk upright, also made childbirth considerably more dangerous and complex. Nevertheless, bipedality is thought to have facilitated the marked advances in tool use and gestural communication that are hallmarks of the human condition.
There is a huge amount of variety in the colours and patterns exhibited by plants and animals. However, most of this variation is fixed at the individual level; only when comparing individuals do we see differences. The ability to change your colour during your lifetime is a trait possessed by only a few animals, which have converged on remarkably similar mechanisms. Colour changes that occur during an animal’s lifetime can occur slowly, with seasonal changes or age (morphological colour change). More dramatically, and more interestingly, some species also have the ability to change their colour or pattern very rapidly, in response to environmental or social conditions (physiological colour change).
One of the most distinctive characteristics of Homo sapiens is our exceptionally large brain, and enhanced cognitive capabilities. In fact, large brains, measured by the encephalisation quotient (EQ), are a characteristic of primates in general, and brain size and complexity has been increasing in the primate lineage for nearly 70 million years. However, this trend is particularly noticeable in the human lineage, and the last 3 million years of hominid evolution have seen the most pronounced increases in encephalisation, with a tripling in brain size. Such a rapid increase in size is extraordinary, especially for an organ so complex. Some areas of the brain have expanded disproportionately, such as the cerebral cortex, which has increased in size by 3 orders of magnitude since our divergence from Chimpanzees. The cerebral cortex accounts for around 85% of total brain volume in humans, and is responsible for complex mental functions.
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