Category: Health & Medicine

[Skip to list of Topics for this Category →]

Convergence is apparent in various situations where organisms have evolved to deal with dangerous threats (e.g. toxins, predators, pathogens) that affect optimal bodily function, or what can broadly be termed 'health'.

Among the examples of health-related convergence presented on the Map of Life, the production of insect-repelling chemicals stands out as one case of special interest. Numerous plants and produce organic compounds to deter insect predators, and in a similar way certain millipedes synthesise benzoquinones that are distasteful to birds and other predators. Mosquitoes can pose a serious threat to the animals that they feed on, and a number of monkeys, Madagascan black lemurs and one bird, the strong-billed woodpecker have independently responded by producing mosquito-repelling chemicals. Humans frequently apply insecticides to protect crops from insect damage, with the predictable result that specific insect proteins targeted evolve to acquire resistance. Interestingly, molecular convergence is frequently observed, whereby the same amino acid substitutions allow proteins in different populations to continue functioning. Immunity from toxic effects also occurs by a convergent molecular mechanism in those animals that are resistant to the lethal effects of saxitoxin and tetrodotoxin. Production of saxitoxin and tetrodotoxin for defence or predation a convergent feature of many organisms (mostly marine) and resistance to toxicity is primarily conferred by precise yet independently acquired amino acid substitutions in sodium voltage-gated channel proteins. Another example of molecular convergence in the area of health relates to alcohol dehydrogenase, which renders alcohol less toxic to the diverse organisms that are exposed to it through eating rotting fruit (or deliberate consumption as in humans). The process of inebriation in fruit flies and mammals show that 'drunken' behaviour is intriguingly parallel in the two groups, and that fruit fly research might yield useful insights into any genetic basis of alcoholism in humans.

Among bacteria that cause disease in humans we find Shigella and Salmonella, two pathogenic strains related to the famous experimental bacterium E. coli. Interestingly, striking convergences have been noted in features such as genome reduction in these pathogenic bacteria. Well known for their troublesome effects on human health, two distantly related species of fungi, Malassezia and Candida have independently evolved to tolerate human skin chemistry. Malassezia is found on the scalp and is correlated with dandruff while Candida can cause systemic irritation and serious problems in those with compromised immune systems.

Innate immune systems themselves appear to have evolved independently in animals and plants, providing a powerful protection against pathogens. Adaptive immune systems are highly specialised, storing 'memories' of previous immune threats and raising targeted defences when specific threats are encountered again. It may seem surprising that such complex immune co-ordination and flexibility could have evolved more than once, but indeed it seems that adaptive immunity has evolved independently in jawless fish, jawed vertebrates and to a degree in some insects.

A final noteworthy case closely linked to optimal health is the phenomenon of sleep, which appears to be a convergent feature of animals that demonstrate complex behaviour, learning and memory. Animals that show true sleep include mammals, birds, octopus and even certain arthropods, such as crayfish and bees.

Go to the top of the page

Topic Title Teaser text Availablity
Nematode antibacterial proteins and invertebrate defensins n/a Not Available
Peroxidases and oxidases n/a Not Available

Not many foods served in a restaurant can kill you, but pufferfish is the exception. Tetrodotoxin, the toxin responsible for such culinary fatalities, reveals a fascinating story of convergent evolution...

Saxitoxin synthesis: from molluscs to algae

Saxitoxin has a similar molecular structure to tetrodoxin and a wide distribution amongst living organisms, with evidence that is has been recruited independently several times.

Dandruff, Malassezia and Candida

The presence of Malassezia does not guarantee dandruff, as this fungus is commonly present on healthy skin, but it evidently central to dandruff production if other key factors support it.

Innate and adaptive immune systems

A vile cough, soaring temperature? When attacked by nasty microbes, our immune system comes in handy. Surprisingly (or not), plants have come up with a very similar solution to dealing with pathogens, but independently...



Evolution of insecticide resistance

There are several varieties of insecticide, and each one is designed to knock out some metabolic or physiological capability of the insect, targeting a specific system.

Not Available
Pathogenic bacteria n/a Not Available
Sleep in animals

Suffering from insomnia? Fruit flies do as well...

Insecticide production: from plants to primates

Application of insecticides, such as against mosquitoes, has been documented in several primates and birds.

Not Available
Elephant response to death

Elephants are extremely unusual in their reaction to the dying and death of their compatriots, which includes attempts at resuscitation and grieving.

Not Available
Alcoholism in mammals and flies

Identification of alcohol tolerance (or lack thereof) in different animal groups is important because alcoholism in humans may have some genetic basis.

Not Available