Battling Beetles

Antlers and horns are usually associated with the male of the species, but sometimes the females bear battle armor.

Female dung beetles have horns that are used in challenging other female dung beetles for dung. Dung beetles lay their eggs in dung, and researchers have found that females with more robust horns produced more offspring than females of similar size but with smaller horns.

Experiments also showed that, unlike males, who may sport extravagant ornament to advertise their superior genetic makeup and suitability as a mate, female ornament does not play a role in sexual selection, at least among dung beetles. So it appears that development of showy weaponry in female dung beetles is related to survival in procuring resources, while in males it functions for survival of a different sort.

Sources: Millus, S., Female beetles ready for dung wars. Science News March 27, 2010

Watson, Nicola and Simmons, Leigh, Proceedings of the royal Society B, March 3, 2010

Watson and Simmons, Behavioral Ecology, March-April, 2010

Photo credit: Sean Stankowski

Charles Darwin, Evolutionary Behavioralist

Darwin’s book, The Expression of the Emotions in Man and Animals, was a foray into applying evolution by natural selection to non-physical traits.

The roots for this book extended back to the birth of Darwin’s own children, and he kept notes on their behavior from birth. Later, he supplemented his personal observations by sending questionnaires to correspondents around the world. With these data he established that some behaviors and emotions are indeed universal, a trait of our species, and as such, subject to evolution through natural selection.

The book was significant for another, technical reason: Darwin included photographs to illustrate different facial expressions, and this was one of the first scientific treatises to include this technology. Darwin thought the photos more objective than drawings. The photo here is Plate II from the book, "grief".

Charles Darwin & Sexual Selection

Here, in his own words, Darwin’s observations of differences between the sexes that led to his hypothesis of sexual selection:

In the several great classes of the animal kingdom - in mammals, birds, reptiles, fishes, insects, and even crustaceans - the differences between the sexes follow nearly the same rules. The males are almost always the wooers; and they alone are armed with special weapons for fighting with their rivals. They are generally stronger and larger than the females, and are endowed with the requisite qualities of courage and pugnacity. They are ornamented with infinitely diversified appendages, and with the most brilliant or conspicuous colours, often arranged in elegant patterns, whilst the females are unadorned. These various structures for charming or securing the female are often developed in the male during only part of the year, namely the breeding-season.

Photo credit: http://www.crbs.umd.edu/crossingborders/ai2008/lessonplans08.html

Charles Darwin & human evolution

Darwin purposely avoided the subject of human evolution in his book Origin of Species, but 12 years later he met the subject head on in The Descent of Man and selection in relation to sex.

Again, Darwin countered Victorian-era assumptions of special creation with his explanation of descent from a common ancestor and evolution through natural selection.

In this book Darwin introduced the concept of sexual selection, a process that explains some features—like the male peacock’s extravagant tail—as adaptations to ensure reproductive success and the continuation of the species.

150 years later we can see that Darwin did not get everything right in the Descent of Man—like his conclusion that men are more highly evolved than women--but his work brought an intellectual framework to the subject of human origins that paved the way for further research.

Image credit: http://commons.wikimedia.org/wiki/File:Human_evolutionary_tree.jpg

Darwin & Orchids

Darwin’s life as a scientist did not end in 1859 with the publication of On the Origin of Species by means of Natural Selection. Three years later he published the results of observations and experiments he had made on orchids, entitled, On the Various Contrivances by Which British and Foreign Orchids Are Fertilised by Insects.

In this book Darwin explained the intimate relationship between orchids and the insects that pollinate them. Darwin described examples of the unique structures that some orchids have that perfectly fit unique structures of the specific insect pollinator for that flower, and he suggested that these complimentary structures existed through a process of co-evolution between the flower and the pollinator as a result of natural selection. Darwin wrote,

“I think this little volume will do good to the "Origin", as it will show that I have worked hard at details'.

Photo: Darwin star orchid. Its existence was predicted by Darwin, 40 years before it was discovered.

It's Darwin Month!

February is Charles Darwin’s birth month, and we will use the occasion to run a series of blogs summarizing the man, his life, and at least some of his contributions to science.

Most folks would probably confess that they know little about Darwin, and odds are that most of what people think they know about him is wrong. For example, one misconception is that Darwin invented the idea of evolution. In his book, On the Origin of species by means of natural selection one of the first things Darwin does is trace the history of thought on change among living things, from Aristotle to his own grandfather.

The word “evolution” does not even appear in Darwin’s writing until later editions of the Origin.

Darwin was not the first person to observe that species evolve, but because of the success of his book--a best-seller in Victorian England--and the robustness of his ideas, he is the best known.