Darwin's Scorecard

Ignorance of inheritance

Darwin didn’t know much about inheritance. That isn’t our claim--it is Darwin’s claim. Darwin frequently made appeals to ignorance when he didn’t have any data to back up his ideas.

The laws governing inheritance are quite unknown; 5

In these chapters I have endeavoured to show, that if we make due allowance for our ignorance 6

if we remember how profoundly ignorant we are. . . 7

if we make the same allowances as before for our ignorance. . . 8

But it deserves especial notice that the more important objections relate to questions on which we are confessedly ignorant; nor do we know how ignorant we are. 9

Darwin didn’t know how inheritance worked. Much of what he thought he knew about inheritance was wrong (as we shall see in a moment). But he argued that even though he didn’t understand how inheritance works, we could be sure that it must work the way he thought it worked. In other words, he argued from faith, not facts. To accept Darwin’s theory, people of his day had to believe in things that nobody understood. To accept Darwin’s theory today, people have to believe in things that are contrary to what modern science has discovered.

Darwin said,

But I am strongly inclined to suspect that the most frequent cause of variability may be attributed to the male and female reproductive elements having been affected prior to the act of conception. 10

Ironically, what he said was true, but what he meant was wrong. It is true that damage to the ovaries or testicles (from radiation or chemical agents) will cause birth defects, which makes the offspring different from other offspring. Scientists routinely subject fruit flies to x-rays and toxic chemicals to damage their reproductive organs in such a way as to increase the rate of mutations so the mutations can be studied.

But that isn’t what Darwin was talking about. He thought life experiences (not x-rays or toxic chemicals) affected sex organs. One of the examples he gave was,

The great and inherited development of the udders in cows and goats in countries where they are habitually milked, in comparison with the state of these organs in other countries, is another instance of the effect of use. 11

Darwin believed that acquired characteristics were inherited because exercise, nutrition, and climate, affected the reproductive organs. Daily milking of a cow would, he thought, produce increased milk-producing hormones in the cow, and these hormones would, through some method of which he was ignorant, affect the ovaries in such a way that its offspring would have more-developed udders.

Modern scientists know that acquired characteristics aren’t inherited. You can go to the gym and workout until you have buns of steel, but any children you conceive have will still have baby-soft butts. Milking a cow doesn’t make her offspring give more milk. Darwin was entirely wrong on this point.

From the facts alluded to in the first chapter, I think there can be little doubt that use in our domestic animals strengthens and enlarges certain parts, and disuse diminishes them; and that such modifications are inherited. 12

Exercise does, to some extent, strengthen and enlarge some parts. Disuse does diminish some parts. But those modifications are not inherited, and therefore unimportant to the evolution of a new species.

I think the common and extraordinary capacity in our domestic animals of not only withstanding the most different climates but of being perfectly fertile (a far severer test) under them, may be used as an argument that a large proportion of other animals, now in a state of nature, could easily be brought to bear widely different climates. 13

In other words, Darwin thought that when an animal is exposed to cold weather, it grows a thicker coat, thicker layer of fat, and has higher metabolism. If the exposure is gradual enough that the cold weather doesn’t kill the animal, these things might indeed happen. But Darwin also believed (without any evidence to support his belief) that the climate would affect male and female reproductive elements in such a way that the animal’s offspring will be born with a thicker coat, thicker layer of fat, and higher metabolism. Darwin got that wrong.

Climate might cause individuals that already have tolerance to cold to survive when individuals without that tolerance die without leaving offspring. After several generations this will result in a breed (or variety) that is tolerant to cold. But, according to our hypothetical situation, the individuals that survived already had the tolerance to the climate. So, it doesn’t answer the question, How did tolerance to cold originate? Darwin thought that the climate caused the tolerance of cold weather to evolve, but he was wrong. Natural selection merely eliminated the individuals that lacked the necessary characteristics. Neither natural selection, nor exposure to cold, produced a new characteristic. It merely eliminates the individuals that lack an already existing characteristic. The ratio of animals with the advantageous characteristic to animals without the advantageous characteristic will change (one could say the ratio evolves), but features don’t change.

Correlation of Growth

Darwin would only allude to what may be called correlation of growth. Although it was only a minor part of his theory, we need to address it. Here is what he said.

There are many laws regulating variation, some few of which can be dimly seen, and will be hereafter briefly mentioned. I will here only allude to what may be called correlation of growth. Any change in the embryo or larva will almost certainly entail changes in the mature animal. In monstrosities, the correlations between quite distinct parts are very curious; and many instances are given in Isidore Geoffroy St Hilaire's great work on this subject. Breeders believe that long limbs are almost always accompanied by an elongated head. Some instances of correlation are quite whimsical; thus cats with blue eyes are invariably deaf; colour and constitutional peculiarities go together, of which many remarkable cases could be given amongst animals and plants. From the facts collected by Heusinger, it appears that white sheep and pigs are differently affected from coloured individuals by certain vegetable poisons. Hairless dogs have imperfect teeth; long-haired and coarse-haired animals are apt to have, as is asserted, long or many horns; pigeons with feathered feet have skin between their outer toes; pigeons with short beaks have small feet, and those with long beaks large feet. Hence, if man goes on selecting, and thus augmenting, any peculiarity, he will almost certainly unconsciously modify other parts of the structure, owing to the mysterious laws of the correlation of growth. 14

His observations are generally correct, but not for the reason he thought. (A modern observation along these lines is that German shepherd dogs tend to have hip problems. ) Although Darwin thought it had to do with a change in the embryo or larva that is somehow related to growth of other features, it actually has a genetic cause that is present from the moment of conception. Modern scientists recognize this phenomenon is a problem associated with inbreeding.

Darwin was not the first scientist to recognize the dangerous side effects of inbreeding. Darwin is known to have studied a 1611 translation of an ancient text that made the exact same observation. 15 If Darwin deserves credit for recognizing correlation of growth, then we must also credit Moses for being an expert in genetics, (or for quoting someone else who was).

What Darwin failed to realize is that inbreeding has undesirable side effects that tend ultimately to limit variation. Correlation of growth actually prevents natural selection from continuing without limit. Dog breeders, horse breeders, corn breeders, and pigeon breeders, are well aware that there are limits to how far the variation will extend. But Darwin incorrectly concluded,

Under domestication we see much variability. This seems to be mainly due to the reproductive system being eminently susceptible to changes in the conditions of life so that this system, when not rendered impotent, fails to reproduce offspring exactly like the parent-form. Variability is governed by many complex laws, -- by correlation of growth, by use and disuse, and by the direct action of the physical conditions of life. 16

Slow though the process of selection may be, if feeble man can do much by his powers of artificial selection, I can see no limit to the amount of change, to the beauty and infinite complexity of the coadaptations between all organic beings, one with another and with their physical conditions of life, which may be effected in the long course of time by nature's power of selection. 17

In other words, he thought that exercise (use and disuse), climate and nutrition (the physical conditions of life), and physical deformation of the embryo caused by correlation of growth, were all mechanisms that produced variations which could be inherited. He thought that there was no limit to this change. He was absolutely wrong on every count!

Intercrossing Prevents Evolution

Darwin was really confused when it came to what he called, intercrossing. For example, he said,

It would be quite necessary, in order to prevent the effects of intercrossing, that only a single variety should be turned loose in its new home. Nevertheless, as our varieties certainly do occasionally revert in some of their characters to ancestral forms, it seems to me not improbable, that if we could succeed in naturalising, or were to cultivate, during many generations, the several races, for instance, of the cabbage, in very poor soil (in which case, however, some effect would have to be attributed to the direct action of the poor soil), that they would to a large extent, or even wholly, revert to the wild aboriginal stock. 18

He thought that if you planted cabbage in poor soil, the cabbage would acquire the ability to grow in poor soil as a direct action of the poor soil. We have already shown that he was wrong about acquired characteristics being inherited. He should have said that a cabbage breeder developed several new varieties of cabbage by carefully controlling the pollination, but that isn’t the error we want to talk about now.

What Darwin correctly realized was that if one planted several varieties of cabbage in the same garden, the cabbages would cross-pollinate each other, and in a generation or two the cabbages would revert to the wild, aboriginal stock. Modern gardeners know not to plant squash and pumpkins close together because the resulting fruit is likely to taste awful. But this is not a recent discovery. Man has known not to plant two kinds of seed in the same field for thousands of years. 19

Darwin’s observation about intercrossing was correct, but he failed to recognize the impact to his theory. If reproductive isolation produced new varieties, the varieties would remain distinct only as long as reproductive isolation was maintained. But it is hard to maintain reproductive isolation in the natural world. As soon as you let your pedigreed dog loose, it will find some other dog of another breed, which will result in a litter of mutts. As long as Darwin’s finches remain isolated on their respective islands, they will remain distinct breeds. But when the barriers are removed, the finches will eventually revert to the wild, aboriginal stock.

The Limit of Change

Darwin failed to realize the difference between varieties and species.

Nevertheless, according to my view, varieties are species in the process of formation, or are, as I have called them, incipient species. How, then, does the lesser difference between varieties become augmented into the greater difference between species? That this does habitually happen, we must infer from most of the innumerable species throughout nature presenting well-marked differences; whereas varieties, the supposed prototypes and parents of future well-marked species, present slight and ill-defined differences. 20

He thought varieties are species in the process of formation, or are, as I have called them, incipient species. What was the evidence? That this does habitually happen, we must infer from most of the innumerable species throughout nature. His reasoning was simply that species exist, and they must have come from somewhere, so they must have come from varieties. That isn’t sound reasoning--it is baseless speculation.

Therefore during the modification of the descendants of any one species, and during the incessant struggle of all species to increase in numbers, the more diversified these descendants become, the better will be their chance of succeeding in the battle of life. Thus the small differences distinguishing varieties of the same species, will steadily tend to increase till they come to equal the greater differences between species of the same genus, or even of distinct genera. 21

I see no reason to limit the process of modification, as now explained, to the formation of genera alone. 22

He didn’t see any reason to limit the process of modification because he didn’t understand genetics and information theory. He recognized the problem of inbreeding (which he called correlation of growth), but didn’t realize that it is associated with a genetic limit. He recognized, but ignored, the fact that intercrossing removes what limited variation actually occurs.

Selective breeding can only remove undesirable genes. It doesn’t create new genes. A species would have to acquire new genes to acquire new characteristics. Neo-Darwinists believe that mutations can create new genes that contain new genetic information. Neo-Darwinists are wrong, too, but that’s beside the point. We are trying to determine if Darwin, not neo-Darwinists, got it mostly right or not.

Darwin thought there was no limit to the amount of variation in a species that could be caused by exercise, diet, and environment. Darwin got this wrong.