There are many possible experiments you could try. Perhaps the most obvious is a series of experiments in which you cut off half a plant's leaves or a mouse's tail and see if the offspring acquire that characteristic.
This has been done!
One scientist cut the tails off of mice for many generations but he never found tailless mice among the offspring. And their tails were no shorter than expected either.

Coming up with a series of observations that would disprove Inheritance of Acquired Characteristics may have been more difficult for you, however, there are many examples among humans. We, as a species, are fascinated with various cosmetic and surgical procedures to identify us as members of our local peer group. Some people traditionally puncture and pierce their bodies in order to be clearly identified as a member of the tribe or as a sign of (cultural) beauty. Some religions also practise body alterations. Baby boys born as Jews are traditionally circumcised. (Their foreskin is removed.) These traditions have been going on for many generations yet no African tribe has evolved premade holes in their bodies and no Jewish family gives birth to boys with missing foreskin. Pierced ears and circumcision are acquired but never inherited characteristics.

These examples disprove the Inheritance of Acquired Characteristics.

Our third and final hypothesis is the one generally accepted as scientific, because it is falsifiable.
It is accepted as "true" because it has yet to be disproven.

Descent With Modification (also called Evolution by Natural Selection or simply Natural Selection) was described by Charles Darwin in his book Origin of Species published in 1859. This theory of evolution was simultaneously developed by another great scientist and naturalist, Alfred Wallace, but Darwin and his supporters presented the idea better. Indeed, this theory is so well accepted as Darwin's that Descent With Modification is often called "Darwinian Evolution".

So, what did Darwin say?

Darwin's theory is based upon two important observations of nature.

  1. Organisms produce far more offspring than can possibly be supported by the ecology (island, river, planet, etc.).
  2. There is a great deal of variation among individual organisms.

So Darwinian evolution is based upon populations and variations.

Let's take a closer look at these two factors.

First populations.

A female cod can (and will) lay thousands of eggs in a single breeding season. If all her offspring survived and her daughters reproduced as successfully as she did, and so on and so on, the oceans would be spilling over with cod in just a few years.
This population explosion would occur with any species if the female created more than a "replacement pair", to replace herself and her mate once they died.
All species produce more offspring than simply the replacements the species need. That means all species lose some individual offspring, but enough survive to keep the species going. (Otherwise they go extinct.)

This graphs show two types of population growth.

If there are no deaths the population grows exponentially and out of control. That is illustrated by the red line.

On the other hand, if deaths occur the population settles to a constant level. That's the blue line.

Populations often start to grow exponentially but sooner or later deaths start to take their toll and the population settles at some level.

A female human is capable of birthing (at least) a dozen children in her lifetime and a few centuries ago it was not uncommon for a woman to have as many as a dozen births before she died.

Why don't women reproduce like that nowadays?

This work was created by Dr Jamie Love and Creative Commons Licence licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.
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