Aristotle was a very well-known and respected scientist. Most people believed spontaneous generation to be true simply because they could not believe that he could be wrong! It took some very forward-thinking scientists to prove that his theory was untrue.

Antoine van Leeuwenhock (1677)What Regnier said is true, I do believe in preformation but the spermist view is correct and he is wrong. I have made a simple magnifying instrument (a microscope) through which I can clearly see a little man – the Homunculus – inside the sperm. I have also seen that there are two types of sperm and so I conclude that the other type contains a female. Here is my drawing of what I saw.

And so the ideas move on……..

Here is a list of other scientists’ work that you may wish to follow up.

Francesco Redi (1626-97) The first person to really question the idea of spontaneous generation. He disproved Aristotle’s theory about maggots forming from rotting meat.

Robert Brown (1854) Brown observed fertilisation for the first time.

Oscar Hertwig (1875) Showed that the nuclei of the sperm and egg fuse in fertilisation. Here was an end to the preformist controversy. He proved that sperm and egg play an equal role in the development of a new living thing.

The human sperm with a Homunculus -

do you think he really saw this?

There are many facts about reproduction that we take for granted but which were less easy for our ancestors to understand. We accept that most plants and animals come into being through the union of two sex cells (sperm and egg) during fertilisation. This process has been photographed many times by using a microscope and so because of this we now believe that this theory is true – it is a fact. But what did people believe back in time? Look through this work and ideas of some of the people who studied the problems of reproduction and inheritance.Aristotle and the Ancient Greeks (over 2000 years ago)My name is Aristotle and I am a famous Greek philosopher and scientist. I have studied many things about the human body and my theory of how a new life is formed is simple. It is called Spontaneous Generation and it shows how a new life can arise from dead or decaying matter. In fact I know that maggots are formed from rotting meat.

Regnier de Graaf (1672)I am a famous Dutch surgeon and I have been looking into how a new life starts. I think that Aristotle was wrong. I believe that there is a tiny person inside a human egg (ovum) and this is activated to grow when covered with the semen from the male during mating. I have called this Preformation. A fellow Dutchman, Antonie van Leeuwenhoek also follows my theory but he believes that it is the sperm from the male that contains this tiny person. Therefore he is a spermist and I am an ovist.

Your Homework Task

Select ONE task from the list below.

1. Explain the meaning of any TWO of the following terms and present it in an interesting way:

Preformation Spontaneous generationspermists

Ovists Homunculus

2.How would you describe the role of the egg and sperm in the development of a new life?

3.What is wrong with the idea of Spontaneous Generation? Could you put arguments forward to disprove this idea?

4.Choose one of the mentioned scientists and find out more about them. Then pretend that you are a reporter for the PERTON NEWS and you are writing an article about them and their work that will shock the world!!

5. Pretend that you are alive in any one of the following periods of time and explain what you have learnt at school about how a new life starts.

The years 1045 1700 1900