Before oxygen came into being, the oldest growing and dividing microbe appeared on Earth nearly 3.8 billion years ago. Taking Earth's age as nearly 4.6 Billion Years, instead of 13.7 from Big Bang, unicellular life appeared nearly 3.8 ago. This percentage is 3.8/4.6 X 100 = 82.6%, of time has life existed on earth.
Half of the guinea pigs will have black fur, while the other half will have white fur. This is because the black is dominant, masking the white gene. But when both genes are recessive, the offspring will have white fur.
