Starting from big bang which took place around 13 - 14 billions years ago and when the earth was formed some 5 billion years ago till 70 000 years ago when present day man made its appearance felt the popluation growth within last 100 years has assumed alarming proportions. Earth and its resources are finite and it cant support and will not support unlimited growth of human populations who are exploiting nature without its regeneration and regeneration of natural resources. If its not a sustainable and renewable energy cycle it wont take billion years for disintegration of life. Protect nature to protect life.