Five years in PopulScience

Albert Einstein

This week we celebrate a small anniversary: five years since this blog was created. In this time, 245 posts have been published. The Spanish version of the blog is a little older: it was created 30 weeks before, in January 2014, and has published 257 posts.

To mark the date by some kind of celebration, I have decided to compute the list of people most mentioned in the blog in these five years. The following table shows the names of the ten people most quoted and the number of times their name has been quoted:

Name	Times quoted in PopulScience
Albert Einstein	42
Isaac Newton	33
Stephen Hawking	20
C.S. Lewis	20
Aristotle	17
Charles Darwin	14
Isaac Asimov	14
Richard Dawkins	12
Plato	10
Ptolemy	9

The end of the selfish gene

The German biologist August Weismann (1834-1914) was one of the most influential biologists of the late nineteenth century. His most important contribution was the theory of germinal plasma, also called in his honor Weismannism. According to this theory, there are two classes of cells in all multi-cellular living organisms (see Figure 1):

Figure 1

• Somatic cells, represented in the figure by an S, that make up most of the body and do not play any role in inheritance.
• Germ cells, represented in the figure by a G: the gametes, ovules and sperm, which pass the genetic information to the next generation.

How the eye evolved

Let us reason about this problem by answering a few questions.

1. Which part of the eye is most essential? The answer is obvious: the retina. If light cannot be detected, the remainder of the eye is useless.
2. Can a retina, on its own, without the rest of the eye, play a useful role? Obviously, yes. Many groups of not too complex animals have ocelli, photo-receptor cells that just react to the presence of light, but cannot form images. Of course, perceiving the presence of light offers advantage against being totally blind. The proof of this: ocelli have appeared independently in at least 40 different animal groups.
3. What is the next step? We also have traces among current animals. The Planaria is a Platyhelminth (flatworm) whose ocelli are located at the bottom of a concavity in its body. Thanks to this, the Planaria not only detects the presence of light, but also, to some extent, the direction it comes from. It is also obvious that being able to perceive the direction of light provides advantage to those who can, against those who cannot.

The eye as an argument about evolution

Schematic diagram of the human eye

The vertebrate eye consists of five parts: cornea (a transparent insulating layer); aqueous humor; crystalline lens (a lens surrounded by muscles that make it possible to achieve a variable focal length); vitreous humor; and retina. The light passes through the cornea and the aqueous humor, is focused by the lens, goes through the vitreous humor and impacts on the nerve cells of the retina, which generate electric signals that the optic nerve transmits to the brain, which forms from them an image of the external world, where the light rays came from. The brain even turns the image around, as it is inverted when projected on the retina.

The complex structure of the eye has always been a problem for evolutionists, and an argument for those opposed to the theory of evolution. Darwin, in Chapter 6 of The Origin of Species, whose title is significant (Difficulties of the theory) dealt with the problem of the evolution of the eye in the following words:

The god of the gaps

In 1977 Pergamon Press published a curious book called The Encyclopedia of Ignorance, which tried to collect, in a collection of articles written by specialists in different areas, most of the problems (then) unresolved in fields such as cosmology, astronomy, particle physics, mathematics, evolution, ecology, biological development, medicine and sociology. Some of these problems have not yet been solved, almost 40 years later; others, like the mystery of the missing neutrinos in the solar radiation, which I mentioned in the previous post, seem to be in the way of being resolved, although this has led to the emergence new problems, as often occurs in science.

Since the nineteenth century, one of the typical accusations of atheists against believers has been that they resort to the god of the gaps, i.e. to use God to explain those things we still don’t know about the structure of the world. We are still far from knowing everything, because science is (and probably always will be) incomplete: there will always be mysteries. Well, believers are accused to rely precisely on the mysteries (the gaps of science) to justify the existence of God. According to this view, God would be nothing more than the deus ex machina of the Greco-Roman drama, who appeared to solve the unsolvable problems where the playwright had entangled his characters. As science advances, the holes will be filled and the need to turn to God will get lower.

Darwin’s mistake

Charles Darwin

Consider the following paragraph by Darwin in The descent of man (chapter 5):

With savages, the weak in body or mind are soon eliminated; and those that survive commonly exhibit a vigorous state of health. We civilised men, on the other hand, do our utmost to check the process of elimination; we build asylums for the imbecile, the maimed, and the sick; we institute poor-laws; and our medical men exert their utmost skill to save the life of every one to the last moment. There is reason to believe that vaccination has preserved thousands, who from a weak constitution would formerly have succumbed to small-pox. Thus the weak members of civilised societies propagate their kind. No one who has attended to the breeding of domestic animals will doubt that this must be highly injurious to the race of man.

It seems incredible that, after a lifetime devoted almost exclusively to meditate on his theory of evolution, Darwin made the mistake of applying it wrongly to humans, as is clearly demonstrated in the paragraph I have just quoted.

Evolution and progress

Friedrich Nietzsche

In the late nineteenth century, many biologists and thinkers, atheists or agnostics, relied on Darwin's theories to build philosophical schools that combined the newly discovered evolution with the eighteenth-century idea of ​​progress, to assert that the history of life and man shows clear traces of indefinite progress, and to predict that such progress will continue indefinitely into the future.

Among the biologists who ascribed to these theories the best known are T.H. Huxley and Ernest Haeckel. The philosophers were many, each one giving rise to a school of his own, often incompatible with those of others: Karl Marx (Marxism), Herbert Spencer (social Darwinism), Auguste Comte (positivism) and Friedrich Nietzsche (nihilism) were the more influential. In their forecasts for the future of evolution, the last-mentioned was the most exalted and predicted that man would soon be succeeded and supplanted by a superior species, the superman.

Outstanding problems in the history of life

Gregor Mendel

In a previous article I wrote about the origin of life and related problems. That is only the first of the outstanding issues regarding evolution. There are many more, for we are far from having an explanation for everything that happened during the history of life.

The theory of evolution through natural selection was first proposed by Darwin and refined by his followers when new discovered biological phenomena solved some of the problems posed since the beginning of the theory:

1.      The laws of heredity (Mendel, 1865).

2.      Mutations (Hugo de Vries, 1900).

3.      The laws of genetics (Thomas Hunt Morgan, early twentieth century).

4.      The synthetic theory of evolution (Simpson, Dobzhansky and others, around 1930)

5.      The transmission of inheritance through DNA (Oswald Avery, 1944).

6.      The structure of DNA and the deciphering of the genetic code (Watson, Crick, Rosalind Franklin and others).

7.      The neutral theory of evolution (Motoo Kimura, 1968).

8.      Punctuated equilibrium (Stephen Jay Gould, 1972).

9.      Epigenetics (early twenty first century).

Rosalind Franklin

The case of the hunting hymenoptera

Jean-Henri Fabre

In 1879, the French entomologist J. H. Fabre studied many species of hymenoptera (solitary wasps and bees) that hunt other insects as food for their larvae. This is the reason for their name (hunting hymenoptera, also called -improperly- parasite hymenoptera). Before laying the eggs, the hymenoptera paralyze the prey by injecting with their sting a drop of poison in every nerve ganglion in the un-centralized nervous system of the prey. In some species, such as Ammophila hirsuta, which hunts caterpillars, the number of ganglions may be large (up to twelve, one per segment in the caterpillar). The hunter seems to know where exactly its prey must be stabbed with the sting.

Once the prey has been paralyzed and the egg laid, the minute larva of the hymenopter digs inside the prey and starts devouring it, showing an apparent innate knowledge of the prey anatomy: it starts feeding on the parts less necessary for life, leaving the vital organs to the last. In this way, the prey does not die and rot, which would make it improper as food and lead to the death of the predator.

Ammophila sabulosa carrying a hunted caterpillar