1. When did life begin on Earth?

2. WHAT IS IIFE?
1.Life is matter that shows certain attributes that include responsiveness, .growth, metabolism, energy transformation, and reproduction. (“Life.” Wikipedia, Wikimedia Foundation, en.wikipedia.org/wiki/life.)
2.Life is a characteristic distinguishing physical entities having biological processes(“Log In.” Britannica School, 16 Nov. 2016, school.eb.com/levels/high/article/ )
3.Life is an organismic state characterized by capacity for metabolism, growth, reaction to stimuli, and reproduction(“Life.” Merriam-Webster, Merriam-Webster,
 So, life is a characteristic distinguishing physical entries having biological process such as responsiveness, growth, metabolism, energy transformation and reproduction.

3. When did life begin Common Known
It is confirmed that the earliest fossils we can trace is dated roughly billion years old, so now we know that life has existed on Earth for at least billion years. So, this became the time that most people think life begun.
(“Life.” Wikipedia, Wikimedia Foundation, en.wikipedia.org/wiki/life.)
(“Log In.” Britannica School, 16 Nov. 2016, school.eb.com/levels/high/article/ )

4. When did life begin
However,  research from scientists at the University of California, Los Angeles, indicates. Living organisms may have existed on Earth as long as 4.1 billion years ago, some 300 million years earlier than previously thought, according to the findings published at the journal Proceedings of the National Academy of Sciences. 
(Marcin, Tim. “When Did Life Begin On Earth? 300M Years Earlier Than Previously Thought, Study Finds.” International Business Times, 20 Oct. 2015, study-finds )

5. Do humans come from star dust?

6. What is stardust?
Stardust is a dusty material found in between the stars. Also a large number of distant stars appearing to the observer as a cloud dust. Many scientist state that we are 93% stardust. But what actually is stardust? Stardust is the exploded remains from a supernova that travel through out the universe only to someday clump together with other stardust and give birth to a new star. Also scientists have established that every element in the periodic table apart from hydrogen is essentially stardust. (“How Much of the Human Body Is Made up of Stardust?” Physicscentral.com, APS Physics, stardust.cfm.)

7. Do humans come from star dust?
Most of the hydrogen in our body floats around in the form of water. The human body is about 60% water and hydrogen only accounts for 11% of that water mass. Even though water consists of two hydrogen atoms for every oxygen, hydrogen has much less mass. Therefore, we can conclude that 93% of the mass in our body is stardust. Just think, long ago someone may have wished upon a star that you are made of.