The Microscope and Revisiting Abiogenesis

Once the microscope was developed, the study of biology was revolutionized. However, mistakes were still made as scientists continued to use observations and hypothesis rather than experimentation.

As we have previously discussed, one of the first major theories in biology was Abiogenesis (the belief that living matter can come from non living matter). Because experiments were never really conducted properly, this theory was supported for hundreds of years.

In the 1700’s, John Needham (an English Biologist) set out to re-examine the theory of Abiogenesis. He designed an experiment, using microscopes, to draw conclusions:

Method / Diagram
He heated a beaker filled with meat broth, to kill any microbes that might exist in the broth. /
He then let the broth sit for two weeks. After the two weeks, he observed that the broth had turned cloudy, and had a bad smell. /
He then examined the broth under a microscope, and saw tiny microbes. /

He concluded that the microbes came from non living broth…therefore, abiogenesis is true. This confused the scientific community because they had just accepted that abiogenesis is false.

WHAT COULD HE HAVE DONE INCORRECTLY?

Lazzaro Spallanzani repeated Needham’s experiment, but modified his method. He boiled the liquid longer, sealed the flasks after boiling, and then let the broth set. He found no microbes. Therefore, he concluded that Abiogenesis did not occur.

People criticized his method, arguing that the “active principle” was missing. Because the jars were sealed, there was no air present. They believed that air was the active ingredient needed to turn non living matter into living matter.

Finally, Louis Pasteur (1822-1895), a French scientist, entered the picture. He had a glassworker develop a special swan-necked flask.

He added broth to the flask and boiled it. Air was able to enter and leave the flask. After letting it set for two weeks, he took a sample, and observed it under the microscope. He found no microbes. Therefore, finally, ABIOGENESIS IS FALSE.

He then tipped the flask, so that some of the broth entered into the neck. After a few days, the broth changed color, and began to give off an odor…Pasteur believed that this proved that the microbes were trapped in the neck of the flask…they were found in the air.