THE AGING PROCESS Part 3
WHAT IS LIFE? HOW AND WHEN DID LIFE BEGIN ON EARTH?
Nobody knows the answers to these questions for sure. Only multiple theories and speculations can be proposed. Most scientists agree that life on Earth did not begin with a single event but through multiple events over extended periods of time.
Scientists who have studied ancient fossils claim that life on Earth began about 3.5 billion years ago as microscopic, simple, primitive cells called “Archaea”. According to one theory, before simple prokaryotic cells formed, massive geophysical events on early Earth must have produced the organic molecules needed for life to begin. Over time, these chemical compounds coalesced into more complex energy-producing compounds, separate compartments, RNA-like structures, and the ability to pass down metabolic information that would become part of primitive life forms.
Archaea, the primitive single-celled organisms still exist on Earth. They cause no disease and are considered the precursors of all life on Earth.
Interestingly, human life also begins as a single cell: a fertilized egg cell called a zygote.
Now let’s look at the most important scientific breakthrough of the past, summarized on a timeline, that enabled scientists to study life and aging at the cellular level.
In the late 16th century, British scientist Robert Hooke and Dutch scientist Leeuwenhoek invented the first hand-made microscope. What they saw surprised them and many others: every tissue and organ in every living organism is made of tiny structures invisible to the naked eye. Robert Hooke called them cells. The discovery of cells drastically changed our understanding of living organisms, biology, and medicine.
Further advances in microscopy led German physicist Max Knoll to discover the electron microscope in 1931. This device uses a beam of electrons, instead of light, to visualize cells and their internal organelles with 1,000 times more resolution, providing a deeper look at and better understanding of cellular functions.
