'I don't need brains,' says the billionaire contemptuously. 'I'm brainy enough myself!' The broker cries out in desperation, 'What, in heaven's name, do you want?' 'Goodness,' is the answer.

There is indeed the possibility that the evolutionary process has, in gray antiquity, bred into us an excess of aggression.

Whenever we find, in two forms of life that are unrelated to each other, a similarity of form or of behaviour patterns which relates to more than a few minor details, we assume it to be caused by parallel adaptation to the same life-preserving function.

I consider early childhood events as most essential to a man's scientific and philosophical development.

In the course of evolution, it constantly happens that, independently of each other, two different forms of life take similar, parallel paths in adapting themselves to the same external circumstances.

When I was about ten, I discovered evolution by reading a book by Wilhelm Boelsche and seeing a picture of Archaeopteryx.

It is a good morning exercise for a research scientist to discard a pet hypothesis every day before breakfast. It keeps him young.

We had better dispense with the personification of evil, because it leads, all too easily, to the most dangerous kind of war: religious war.

The bond with a true dog is as lasting as the ties of this earth will ever be.

Ethologists are often accused of drawing false analogies between animal and human behaviour. However, no such thing as a false analogy exists: an analogy can be more or less detailed and, hence, more or less informative.

Every man gets a narrower and narrower field of knowledge in which he must be an expert in order to compete with other people. The specialist knows more and more about less and less and finally knows everything about nothing.

Historians will have to face the fact that natural selection determined the evolution of cultures in the same manner as it did that of species.

I believe that present day civilized man suffers from insufficient discharge of his aggressive drive.

Practically all animals which move fast in a homogeneous medium have found means of giving their body a streamlined shape, thereby reducing friction to a minimum.

We do not take humor seriously enough.

Evil, by definition, is that which endangers the good, and the good is what we perceive as a value.

I grew up in the large house and the larger garden of my parents in Altenberg. They were supremely tolerant of my inordinate love for animals.

Barking dogs occasionally bite, but laughing men hardly ever shoot.

Most of the vices and mortal sins condemned today correspond to inclinations that were purely adaptive or at least harmless in primitive man.

I owe undying gratitude to my patient parents.

The father-mother family with two children isolated in a city flat is already insufficient.

I have found the missing link between the higher ape and civilized man; it is we.

Truth in science can be defined as the working hypothesis best suited to open the way to the next better one.

From a neighbour, I got a one-day-old duckling and found, to my intense joy, that it transferred its following response to my person. At the same time, my interest became irreversibly fixated on water fowl, and I became an expert on their behaviour even as a child.