Showing posts with label Charles Darwin. Show all posts
Showing posts with label Charles Darwin. Show all posts

26 September 2012

Transformations


I'm rereading The Origin and, geekishly, really enjoying this sort of thing (from Morphology, Chapter XIV):
Most physiologists believe that the bones of the skull are homologous with — that is, correspond in number and in relative connexion with—the elemental parts of a certain number of vertebræ. The anterior and posterior limbs in all the members of the vertebrate classes are plainly homologous. So it is with the wonderfully complex jaws and legs of crustaceans. It is familiar to almost every one, that in a flower the relative position of the sepals, petals, stamens, and pistils, as well as their intimate structure, are intelligible on the view that they consist of metamorphosed leaves, arranged in a spire. In monstrous plants, we often get direct evidence of the possibility of one organ being transformed into another; and we can actually see in flowers during their early development, as well as in crustaceans and many other animals during their embryonic states, that organs, which when mature become extremely different, are at an early stage of growth exactly alike.
Darwin asks questions such as: 'Why should the brain be enclosed in a box composed of such numerous and such extraordinarily shaped pieces of bone?' And then shows how natural selection is the necessary explanation.

22 April 2009

Dancing

New Scientist reports that 'dancing' Volvox algae can 'waltz' and 'minuet'. [1]



It's another reminder that while green, red and brown algae are often called 'plants', some of them have properties that are almost 'animal'-like. [2] Some dinoflagellates, for example, have simple eyes to hunt for food. [3]

And at a macro scale, kelp (which are brown algae) do remarkable things, as Charles Darwin saw:
The number of living creatures of all Orders, whose existence intimately depends on the kelp is wonderful.

A great volume might be written, describing the inhabitants of one of these beds of seaweed….I can only compare these great aquatic forests of the southern hemisphere, with the terrestrial ones in the inter-tropical regions. Yet if in any country a forest was destroyed, I do not believe nearly so many species of animals would perish as would from here, from the destruction of the kelp. [4]


[1] Dancing Volvox: Hydrodynamic Bound States of Swimming Algae by Knut Drescher, Kyriacos C. Leptos, Idan Tuval, Takuji Ishikawa, Timothy J. Pedley and Raymond E. Goldstein (pdf).

[2] Other 'simple' protists such as forams display remarkable properties too. Lynn Margulis is a microbiological William Blake in her vision of these creatures:
Large single-celled forams choose from brightly colored sand grains the correct ones with which to make shells. Aware of shape and color, they make choices and reproduce their kind. Awareness in some form has been naturally selected for at least 550 million years. For me, our spirituality and moral nature help perpetuate our living communities, just as similar attributes aided previous living communities whose evolution is chronicled in the fossil record.
[3] "By most definitions...the planktonic dinoflagellate, Erythropsidium, must have among the smallest of eyes, since the creature is only 50–70 μm in diameter." -- from You are what you eat by I R Shwab. Others with eyes include: Peridinium foliaceum and P. balticum. See Ultrastructure of Microalgae: nonphotosynthetic plastids.

[4] The Voyage of Beagle, Chapter 11:
Almost all the leaves, excepting those that float on the surface, are so thickly incrusted with corallines as to be of a white colour. We find exquisitely delicate structures, some inhabited by simple hydra-like polypi, others by more organised kinds, and beautiful compound Ascidiæ. On the leaves, also, various patelliform shells, Trochi, uncovered molluscs, and some bivalves are attached. Innumerable crustacea frequent every part of the plant. On shaking the great entangled roots, a pile of small fish, shells, cuttlefish, crabs of all orders, sea-eggs, starfish, beautiful Holothuriæ, Planariæ, and crawling nereidous animals of a multitude of forms, all fall out together. Often as I recurred to a branch of the kelp, I never failed to discover animals of new and curious structures.
Darwin was writing about kelp in cool southern waters. But kelp 'forests' have recently been discovered in deep tropical waters too. It's thought that these may act as refugia under some conditions of climate change.

29 January 2009

Common descent

Rather than being morally subversive, as his Christian critics claim, Darwin's achievement was morally grounded. Rather than being a dispassionate practice, his science had a humanitarian drive. It made brothers and sisters not only of all human races, but of all life.
-- from Darwin the abolitionist by Adrian Desmond. [1]


(images: Selk'nam U Onas: 1, 2)

P.S. 9.45am: an article has just gone up on the BBC web site

Footnote:

1. David Remnick writes:
[John] Lewis read his Bible and on Sundays tuned in to WRMA, the gospel station out of Montgomery, to hear the Soul Stirrers and the Five Blind Boys of Mississippi. Lewis was a soulful, intelligent, and eccentric child. When religious feeling washed over him, he began visiting the henhouse out back to preach to the Dominiques and the Rhode Island Reds. The chickens composed his ministry: Lewis baptized new chicks; he raised and fed them; he buried the dead under a mound of wildflowers. As Lewis wrote many years later in his autobiography, “Walking with the Wind,” he was a lonely searcher learning compassion for God’s creatures.

9 January 2009

1859 and all that

John Whitefield considers the woodpecker at the start of his Blogging 'The Origin'.

Did Darwin know about the Woodpecker's fellow Piciformes, the Honeyguides?

Science magazine begins a blog on the origin of life.

5 January 2009

Twilight souls

Having proved men and brutes bodies on one type: almost superfluous to consider minds. [1]
Almost but not quite:
He who understands baboon would do more towards metaphysics than Locke. [2]
What, then, to make of the 'new, scientific' study of morality by the likes of Marc Hauser, which may point to something like this:
the science [sic] of morality may bring into doubt some of our most deeply ingrained cultural perceptions about right and wrong. We’ll have new, richer opportunities to examine our actions in the presence of consequences. We probably won’t like what we see. [But] those awkward realizations may be the greatest value of moral science. [3]
How far are we here from:
No man can ever attain to anywhere near a true conception of the subconscious of man who does not know primates under natural conditions. [4]
Carlo Fausto [5] quotes Friedrich Nietzsche:
Our body is, after all, only a society constructed out of many souls.
and Mia Couto:
In Lua-do-Chão, there is no word to say “poor.” One says “orphan.” This is true misery: to have no kin.

Footnotes

1. Charles Darwin, Notebooks on transmutations of species.

2. Darwin, 1838 notebook.

3. Reinventing Morality, a review of Moral Minds (2006).

4. Eugène Marais, in a letter from 1935, republished in an introduction to the The Soul of the Ape by Robert Ardrey. Ardrey was an advocate of the now unfashionable 'killer ape' hypothesis. More popular these days may be the 'kind ape' hypothesis. ('Twilight souls' is a term used by Marais to describe the Chacma baboons of the Waterberg. There is evidence that Australopithecus africanus and, later, Homo erectus lived in the Waterberg.)

5. Feasting on People: Eating Animals and Humans in Amazonia, 2007. DOI: 10.1086/518298


Image: Gaza

26 November 2008

An eye "very imperfect and simple"

The brittlestar has an entire carapace pitted with optically tuned calcite crystals.[1]

The photo is featured in a Darwin 'special' in Nature. The editorial says:
An even more likely development [in the next 50 years than the discovery of life beyond Earth] is that life will be created de novo here on Earth. The first experiments in whole-organism synthetic biology, such as the synthetic mycoplasma being worked on at the J. Craig Venter Institute in Rockville, Maryland, will cleave quite closely to the designs already developed by natural selection. But there are already schemes for going further — for using different genetic codes, for example. Although the synthesis of complex organisms might remain the stuff of fantasy for some time, new ways of building self-replicating, one-genome, one-cell organisms seem quite plausible. The development of creatures born from an idea, not an ancestor, will undoubtedly provide new insights into evolution, not least because the proclivities of such creatures to evolve will need to be kept in check.

[1] P.S. 28 Nov: There's a note on brittlestars by Mark H at Daily Kos

2 June 2008

Entangled

...it is curiosity, scientific curiosity, that has delivered us genuine, testable knowledge of the world and contributed to our understanding of our place within it and of our nature and condition. This knowledge has a beauty of its own, and it can be terrifying. We are barely beginning to grasp the implications of what we have relatively recently learned.
-- from The day of judgement by Ian McEwan.

McEwan also writes:
Natural selection is a powerful, elegant, and economic explicator of life on earth in all its diversity, and perhaps it contains the seeds of a rival creation myth that would have the added power of being true - but it awaits its inspired synthesiser, its poet, its Milton.
But I don't think summoning Milton is helpful. It's not just that we have already had Darwin (who, if you have to stretch for a comparison, is more like natural selection's Homer) but that Darwin, his predecessors and successors, are part of an encounter, a conversation, a long argument for which the entrance requirement need be no more than, for example, stopping to listen, really listen, to birdsong -- plus a readiness to be open to where evidence leads.