Charles Darwin & the action of earthworms

It seems obvious to us now, if we stop to think about it, but in Darwin’s day people did not appreciate the role earthworms played in aerating and fertilizing soil, and the effect that all that burrowing had on displacing objects-- a headstone, the foundation of a house.

Darwin performed an experiment in which he buried a layer of pieces of coal at a known depth, then returned 20 years later to check the distribution of the coal pieces to find that they had indeed been mixed more deeply into the soil. Darwin used coal because it is distinctive from the native soil and chalky bedrock of his garden.

Of the earthworm Darwin wrote, "...it may be doubted if there are any other animals which have played such an important part in the history of the world as these lowly organized creatures."

In 2009, researchers returned to the garden at Down House and re-excavated the coal layer, and found it, 100 years after Darwin’s original experiment:

http://www.npr.org/templates/story/story.php?storyId=100627614

Photo: illustration from "Formation of Vegetable Mould..." showing the buried coal, from http://darwin-online.org.uk/converted/published/1882_Worms_F1364/1882_Worms_F1364_fig150.jpg

Charles Darwin & the Natural History of...worms

The last scientific treastise Darwin published was entitled, “The Formation of Vegetable Mould Through the Action of Worms, With Observations on Their Habits". Despite the title, the book sold more copies than On the Origin of Species during Darwin’s lifetime.

In Darwin’s day the action of earthworms, and the natural history of earthworms was not known. Darwin did experiments to determine what senses earthworms possessed.

In one of these experiments, he put a pot of earthworms near the family piano and struck a note (Darwin even tells us which note). The worms did not respond. He repeated the experiment with the pot placed on the piano, which did engender a response and revealed how earthworms sense sound through vibrations.

No big grants required to do this research, you could reproduce Darwin’s technique in your own home.

Photo credit: http://ed101.bu.edu/StudentDoc/current/ED101sp09/eflukes/

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 & Plants

After publishing the Origin of Species, Darwin moved into what might be called his botany phase, and he published 7 books on various aspects of variation in plants. In his autobiography Darwin explained his interest in climbing plants:

“I was led to take up this subject by reading a short paper by Asa Gray…. He sent me seeds, and on raising some plants I was so much fascinated and perplexed by the revolving movements of the tendrils and stems, which movements are really very simple, though appearing at first very complex, that I procured various other kinds of Climbing Plants, and studied the whole subject.

Darwin could make sense of this behavior in terms of natural selection. He wrote, “some of the adaptations displayed by climbing plants are as beautiful as those by Orchids for ensuring cross-fertilisation.”

Photo credit: http://darwinsflowers.files.wordpress.com/2009/07/10-4-1_darwin_movements.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.

Darwin and Insectivorous plants

Odd plants fascinated Darwin. In his spare time he took up the subject of carnivorous—or more properly, insectivorous, plants.

It was sixteen years from his first observations to publication of his book on Insectivorous Plants, and in his autobiography Darwin put a positive spin on the length of time it took him to publish. He wrote.

"The delay in this case, as with all my other books, has been a great advantage to me; for a man after a long interval can criticise his own work, almost as well as if it were that of another person. The fact that a plant should secrete, when properly excited, a fluid containing an acid and ferment, closely analogous to the digestive fluid of an animal, was certainly a remarkable discovery."

Photo credit: http://darwinsflowers.files.wordpress.com/2009/09/5-3-4_insectivorous_plants_drosera1.jpg

Charles Darwin & barnacles

After returning from his Beagle Voyage and before writing Origin of Species, Charles Darwin labored to establish himself as a bona fide scientist. It was all well and good to send reports back from the Beagle and publish an account of his observations during the voyage, but another thing entirely to publish a scientific treatise.

Darwin chose as his subject an animal that he had encountered on the Beagle voyage—barnacles. Most people know barnacles as an encrusting menance on their boats or docks. These strange arthropods live free as larvae, but as adults some settle on a hard surface and form a hard calcite shell around them, others live attached by flexible “stems”.

Darwin spent 8 years laboring over his microscope dissecting the tiny animals. It was all his children knew of his research during that time, and they are reported to have asked their playmates, “where does your father do his barnacles?” Darwin published several monographs on living and fossil barnacles.

Photo credit: http://www.darwininlondon.co.uk/index/darwin-in-london/darwin-and-evolution/

Charles Darwin, Ornithologist

Although Charles Darwin had no formal training in ornithology, the collections of birds he made during his time on the Beagle, breeding experiments he did with his own chickens and pigeons, and observations he made on various habits of birds earn him a place of honor alongside more traditionally trained avian researchers.

Darwin sent back nearly 500 bird specimens from the Beagle voyage, and 38 new bird species were described on the basis of these specimens.

Darwin did not identify the birds himself, but delegated that task to John Gould, the preeminent ornithologist of his day. Even so, the birds that showed variation from island to island in the Galapagos archipelago bear the name “Darwin’s finches” in honor of the man who collected them and explained the significance of their inter-island variation as a manifestation of natural selection.

For Valentine's Day: Charles + Emma

Charles Darwin to his betrothed Emma Wedgwood: (January, 1839)

"I think you will humanize me, & soon teach me there is greater happiness, than building theories, & accumulating facts in silence & solitude. My own dearest Emma, I earnestly pray, you may never regret the great, & I will add very good, deed, you are to perform on the Tuesday: my own dear future wife, God bless you."

Emma, describing Charles to a favorite aunt, November, 1938:

He is the most open, transparent man I ever saw, and every word expresses his real thoughts. He is particularly affectionate . . . and possesses some minor qualities that add particularly to one's happiness, such as not being fastidious, and being humane to animals."

They married, January 29, 1839; Charles was 30. Their marriage lasted until Charles’ death at the age 73 (April, 1882).

Charles Darwin, Paleontologist

Along with collecting modern plants and animals during his sojourn on the Beagle, Charles Darwin collected fossils.

He is credited with being the first scientist to examine fossils in the Falkland Islands, where he collected fossil brachiopods, but he is better remembered for the large bones of extinct fossil mammals that he found on his excursions in Patagonia, mastodon, giant ground sloths called Megatheria, and the armadillo-like Glyptodon, and fossil horses, which previously were unknown in the Americas.

Darwin sent his fossils back to England, where the leading British anatomist of the day, Richard Owen, described and published Darwin’s finds. Darwin’s paleontological training continued after he returned from the Beagle voyage, and he became an expert on fossil barnacles.

Image: reconstructions by Richard Owen based on fossils collected by Charles Darwin.

Happy Birthday, Chuck!

On February 12, 1809, Charles Robert Darwin was born, the 5^th of six children of Robert and Suzanna Darwin. Robert Darwin was a well-known physician, and Suzanna was a daughter of the pottery magnate Josiah Wedgwood, so the young Charles and his siblings grew up in comfortable circumstances, although Darwin’s mother died when he was 8 and he was raised by his three older sisters.

Charles was not an avid student of the classical education he was exposed to in grammar school, and found himself adverse to his father’s line of work. After Charles dropped out of medical school in Edinburgh, his father despaired, that "You care for nothing but shooting, dogs, and rat-catching, and you will be a disgrace to yourself and all your family.”

Happily, Charles Darwin found his life’s avocation and his accomplishments outlived the folly of his youth.

Image: The cover of Nature magazine, a family portrait of Charles and "friends"

Charles Darwin, Marine Geologist

Atolls are circular coral reefs that enclose a lagoon. Many atolls are found in deep ocean waters, far from continental shorelines, and their formation had long been a mystery.

Charles Darwin encountered a number of atolls during the 5-year Beagle voyage, and after observing the variety of coral reef forms, from fringing reefs ringing volcanic islands, to the circular atolls seemingly rising from the sea floor without benefit of a companion island, he puzzled out their formation.

Darwin correctly interpreted these different reef forms as having a common origin, both starting out as a reef in the shallow waters around a newly formed volcanic island. When volcanism ended, the island volcano began to sink. The coral had to grow upward to remain in shallow water for its survival. As the volcano subsided beneath the waves, the ring of coral that once marked its perimeter remained as an atoll.

Photo credit: http://www.coral-reefs.org/Apron-Fringing-Barrier-Patch-reef.html

Charles Darwin, Geologist

Although more widely remembered for his contributions to the biological sciences, Charles Darwin first made his scientific reputation as a geologist.

His formal geological training was limited, but intense; he accompanied the eminent geologist Adam Sedgwick "geologising", that is,describing and mapping the rocks of Wales and learning the ways of the field geologist.

A few months later Darwin was on board the Beagle, with a volume of Charles Lyell’s new book, Principles of Geology. Lyell was the foremost geologist of the day. With this as his guide, Darwin made observations during the voyage that led to publications on the formation of coral reefs and volcanic islands and the geology of South America, contributions that still stand, today.

Photo: Rocks collected by Charles Darwin during his voyage on the Beagle. credit: http://www.flickr.com/photos/gruts/3802735409/

Beetle mania

Charles Darwin’s interest in natural history goes back at least to his days as a college student, although not as an area of study but as an avid hobby.

While a student at Cambridge Darwin took up the Victorian mania for collecting beetles. One day he had collected two beetles, one in each hand, when he spied a third new kind, and in his words, “I popped the one which I held in my right hand into my mouth. Alas! It ejected some intensely acrid fluid, which burnt my tongue so that I was forced to spit the beetle out, which was lost, and was the third one.“

Despite that miscue, Darwin’s beetle-collecting hobby laid his foundation in collecting, identifying and classifying natural history specimens, and taught him something about proper field collecting techniques.

Photo credit: http://www.ent.iastate.edu/imagegal/coleoptera/dogbane/dogbane_beetle.html

Darwin & the Beagle

The seminal event in Charles Darwin’s life was his 5-year voyage around the world on the HMS Beagle.

Darwin kept extensive notebooks of his observations on the plants, animals, fossils, and rocks of the areas he visited.. Darwin’s voyage is most widely remembered for the visit to the Galapagos Islands off the coast of Ecuador, and for the unique animals that inhabited each island, like the marine iguanas, huge tortoises, and birds, but during the voyage Darwin also made the first geological maps of parts of South America, discovered fossils of previously unknown species of extinct South American mammals, and figured out how coral atolls formed.

Darwin returned to England with observations enough to occupy his thoughts for the rest of his long life.

Photo credit: http://theora.com/images/HMS%20Beagle.jpg

A blog-sized bio

Charles Darwin was born in Shrewsbury, England, February 12,1809, 201 years ago, the son of a wealthy physician.

Across the Atlantic, Abraham Lincoln was born the same day in a log cabin in Kentucky.

Darwin was expected to follow in the footsteps of his father, but, it became clear that he did not have the temperment to witness surgery without anesthetics. His father enrolled him at Christ’s College, Cambridge (1827) to study to become a country parson, but Darwin never became a clergyman.

Darwin had a long-abiding interest in natural history, and one of his early passions was beetle collecting, which was all the rage in Victorian England. As the son of a gentleman and someone with with science training, Darwin was invited to serve as a companion to the captain of the HMS Beagle . He was 22.

The 5-year voyage proved to be the turning point for Darwin, who returned to England with notebooks full of observations occupied his thoughts for the rest of his life.

Darwin & God

Because Darwin advocated natural processes for explaining life on Earth, rather than invoking the special creation of every organism by a omniscient being, another widely held misconception about Darwin was that he did not believe in God.

In fact, Darwin was a deeply devout man who studied to be a clergyman at Cambridge, but who also had his faith severely tested by several personal tragedies including the death of three of his children.

Near the end of his life, Darwin described himself as an agnostic—one who concludes that God is "unknowable", that humans cannot prove or disprove the existence of a God. He wrote, ""I cannot pretend to throw the least light on such abstruse problems. The mystery of the beginning of all things is insoluble to us; and I for one must be content to remain an agnostic."

Darwin never lost his sense of wonder at the beauty and intricacy of the natural world and strove to uncover the natural laws that resulted in what he described at the end of his book “Origin of Species” as “endless forms most beautiful"

Photo credit: http://caxton.emich.edu/guide/images/darwin-god.jpg

The human-ape thing

Probably the most widely propagated misconception about Darwin is that he said humans evolved from apes.

What Darwin actually wrote was that all life is descended from a common ancestor. This idea makes humans very distant relations to bacterial slime, and closer relations to chimpanzees and gorillas. It means that humans and other primates share a common ancestor and are therefore more closely related to each other than to other groups (like reptiles or fish), not that one group gave rise to the other.

Darwin understood that humans share a common ancestor with apes in the distant geological past, and this conclusion has been verified through modern DNA studies that show chimpanzees to be our closest relations.

Photo credit: www.philadelphia-reflections.com/images/darwin.jpg

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.