Acquired characteristics is an ancient idea and goes by several names. The ideas behind this term are also called the Law of Use and Disuse and Lamarckianism after the French scientist Jean-Baptiste Lamarck. The idea behind acquired characteristics is that if an animal “acquired” a trait in its lifetime, it would be passed to its offspring.
Common analogies to explain this idea include the idea that if a horse had large muscles through hard and strenuous work, its offspring would inherit these muscles. However, the Law of Use and Disuse also meant that if an animal stopped using some part of its body, it would not manifest in the offspring. If we follow this line of thinking, if the person who cannot use their sense of smell has children, then this implies that the children will not be able to smell either. This is possible but not guaranteed.
Charles Darwin also adopted acquired characteristics in the development of his Theory of Evolution. However, a few years after his death, August Weisman conducted an experiment using mice. In the experiment, Wiesman cut off the tails of the mice and then had the mice reproduce. The hypothesis was if the parental mice did not have tails, then the offspring would not have tails.
After cutting off the tails of mice for 20 generations, Wiesman found that the offspring were always born with tails. This simple experiment disproves the ideal of disuse and, by implication, the use aspect as well. Naturally, all this was happening when an understanding of genetics was in its infancy and thus did not wholly negate Darwin’s Theory of Evolution.
One of the main pillars of evolution is natural selection which states that the strong reproduce and pass on their traits to their offspring and the weak are not as successful for this. Opponents of evolution say that natural selection only selects variation within a species and does not create or generate new species. For example, a dog change color, grow larger or smaller, faster or slower, but it is still a dog. The local environment plays a role in manifesting traits, but it does not necessarily create new genes.
The same argument is supported by artificial breeding. People can change the appearance and even the behavior of animals through breeding. Racehorses, show dogs, milk-producing cows are all results of artificial breeding. Yet, in each example, a horse is still a horse, a dog is a dog, and a cow is still a cow.
There are also limits on variability. For example, there are natural limits in place genetically for animals and plants in terms of such traits like size, color, shape, etc. For example, apples range in size from that of a golf ball to up to four pounds. Whether an apple can evolve to the size of a ton over the course of millions or billions of years is a hypothesis that no scientist will live long enough to test.
Mutations happen naturally, but for an animal to grow a tail or lose an eye or develop the ability to fly, it would take more than one error in a long line of genetic code. Instead, it would take the changing of thousands of letters that have to be wrong in the right location and the right sequence.
The probability of this happening is not zero, and it could happen over millions of years. This requires a goal-directed approach that is being conducted randomly. It also assumes that the environment remains highly unchanged for long periods of time. This means no major changes in the climate, no catastrophic natural disasters, no dangerous diseases, etc. The changes also must be beneficial, and the organism must be lucky enough to reproduce, which is not a given—considering the time required and the need for some general stability, it would be difficult to conduct an experiment that confirms this.