Transcript Diapositiva 1

REBUILDING THE HEART
IN DARWIN’S YEAR
José M. Sánchez Ron
For Darwin, Nature was a great puzzle,
formed by pieces coming from disciplines
as various as embryology, morphology,
taxonomy, anatomy, zoology, botany,
geology, biogeography, palaeontology,
variations of animals and plants induced by
domestication, hereditary mechanisms and
human psychology
DARWIN’S BOOKS
- The Voyage of the Beagle (1839)
- The Zoology of the Voyage of the Beagle (editor), 5 parts in 3 volumes (18401843)
- The Structure and Distribution of Coral Reefs (1842)
- Geological Observations on the Volcanic Islands visited during the voyage of
H.M.S. Beagle (1844)
- Geological Observations on South America (1846)
- A Monograph of the Sub-Class Cirripeada (vol. 1: The Lepadidae; or
Pendunculated Cirripides [1851]; vol. 2: Sessile Cirripedes [1854]), A Monograph
of the Fossil Balanidea and Verrucidae (1854)
- On the Origin of Species by Means of Natural Selection, or the Preservation of
Favoured Races in the Struggle for Life (1859)
- On the Various Contrivances by which British and Foreign Orchids are Fertilised
by Insects, and on the Good Effects of Intercrossing (1862)
- The Variation of Animals and Plants under Domestication (1868)
- The Descent of Man, and Selection in Relation to Sex (1871)
- The Expression of Emotions in Man and Animals (1872)
- Insectivorous Plants (1875)
- The Effects of Cross and Self Fertilisation in the Vegetable Kingdom (1876)
- The Different Forms of Flowers on Plants of the Same Species (1877)
- The Power of Movement in Plants (1880)
- The Formation of Vegetable Mould through the Action of Worms with
Observations on their Habits (1881)
Charles Darwin, The Origin of Species (1859):
“Can… be thought improbable, seeing that variations
useful to man have undoubtedly occurred, that other
variations useful in some way to each being on the
great and complex battle of life, should sometimes
occur in the course of thousands of generations? If
such do occur, can we doubt… that individuals having
any advantage, however slight, over others, would have
the best chance of surviving and of procreating their
kind? On the other hand, we may feel sure that any
variation in the last degree injurious would be rigidly
destroyed. This preservation of favourable variations
and the rejection of injurious variations, I call Natural
Selection.”
“Variations useful… on the great and complex battle of life”.
“Individuals having any advantage, however slight, over others”.
“Preservation of favourable variations and the rejection of injurious
variations”.
Does this mean that Natural Selection acts only in the positive,
improving species?
Also, in The Descent of Man (1871), Darwin wrote: “Beneficial
variations of all kinds will thus, either occasionally or habitually, have
been preserved, and injurious ones eliminated.”
However, improvement, is a time-dependent concept. Timedependent because natural selection arouses from changes in some
of the conditions in which species live, and conditions, physical
conditions change on the course of time.
Darwin was well aware that the “improvements” produced by evolution entail
a manifold of consequences. For example, the action of evolution on organs
may originate rudimentary or atrophied organs.
The Origin of Species:
“Organs or parts… bearing the stamp of inutility, are extremely common
throughout nature. For instance, rudimentary mammae are very general in the
males of mammals: I presume that the ‘bastard-wing’ in birds may be safely
considered as a digit in a rudimentary state… [These] rudimentary organs [not
entirely developed, may] sometimes retain their potentiality… An organ useful
under certain conditions, might become injurious under others, as with the
wings of beetles living on small and exposed islands; and in this case natural
selection would continue slowly to reduce the organ, until it was rendered
harmless and rudimentary”.
Charles Darwin, The Descent of Man (1871):
“Man in the rudest state in which he now exists is the more dominant
animal that has ever appeared on the earth. He has spread more
widely than any other highly organised form; and all others have
yielded before him. He manifestly owes this immense superiority to his
intellectual faculties, his social habits, which lead him to aid and defend
his fellows, and to his corporeal structure. The supreme importance of
these characters has been proved by the final arbitrament of the battle
for life. Through his powers of intellect, articulate language has been
evolved; and on this his wonderful advancement has mainly depended.
He has invented and is able to use various weapons, tools, traps, &c.,
with which he defends himself, kills or catches prey, and otherwise
obtains food. He has made rafts or canoes on which to fish or cross
over the neighbouring fertile islands. He has discovered the art of
making fire, by which hard and stringy roots can be rendered
digestible, and poisonous roots or herbs innocuous… These several
inventions, by which man in the rudest state has become so preeminent. Are the direct result of the development of his powers of
observation, memory, curiosity, imagination, and reason.”
“Evolution has no eye for the future –it does not
operate with a view to the attainment of
teleological ends or typological goals. In particular,
neither evolution nor the presence of particular
characteristics can properly be characterized as a
steady march of progress towards traits beneficial
(in our minds) to the species as a whole.”
(N. Shanks and R. A. Pyles)
DARWINIAN MEDICINE
“One basic tenet of Darwinian medicine comes
from adaptationist thinking, that diseases arise
because humans exist in a mismatch between
the current world and the world in which our
species evolved and adapted, and that humans
suffer from a series of trade-offs between high
fitness in the pass and reduced fitness in the
present.”
(Michael Antolin, 2009)
The heart, an “atrophied organ”?
The role of stem cells
The Variation of Animals and
Plants under Domestication
(1868)
“It may be convenient fist briefly to discuss that co-ordinating an
reparative power which is common, in a higher or lower degree, to all
organic beings, and which was formerly designated by physiologists as
the nisus formatives.
Blumenbach and others have insisted that the principle which permits
a Hydra, when cut into fragments, to develop itself into two or more
perfect animals, is the same with that which causes a wound in the
higher animals to heal by a cicatrice. Such cases as that of the Hydra
are evidently analogous with the spontaneous division or fissiparous
generation of the lowest animals and likewise with the budding if plants.
Between these extreme cases and that of a mere cicatrice we have
every gradation. Spallanzani, by cutting off the legs and tail of a
Salamander, got in the course of three months six crops of these
members... At whatever point the limb was cut off, the deficient part, and
no more, was exactly reproduced.”
“Even with man, as we have seen en the twelfth chapter, when treating
of polydactylism, the entire limb whilst in a embryonic state, and
supernumerary digits, are occasionally, though imperfectly, reproduced
after amputation… This power of regrowth does not, however, always
act perfectly: the reproduced tail of a lizard differs in the forms of the
scales from the normal tail: with certain Orthoptereous insects the
large hind legs are reproduced of the smaller size: the white cicatrice
which in the higher animals unites the edges of a deep wound is not
formed of perfect skin, for elastic tissue is not produced till long
afterwards.’ The activity of the nisus formatives,’ says Blumenbach, ‘is
I an inverse ratio to the age of the organised body.’ To this may be
added that its power is greater in animals the lower they are in the
scale of organisation; and animals low in the scale correspond with the
embryos of higher animals belonging to the same class... Salamanders
correspond in development with the tadpoles or larvae of the tailless
Batrachians, and both posses to a large extent the power of regrowth;
but not so the mature Batrachians.”