When I think of evolution, I think of small changes over millions of years, but not so for the hardy tomcods of the once heavily polluted Hudson river. Deadly PCBs (polychlorinated biphenyls) were discharged to the river by General Electric Co between 1947 and 1976. This naturally had a deadly impact on the inhabitants, with the tomcod being hit quite hard, as they are filter feeders (PCB contaminants settle on the bottom river bed ). Their life span was reduced from an average 7 years to 2 years and many suffered from tumours.
However, they are fighting back and have evolved to be resistant to the toxin (unlike their counterparts in other ecosystems). Studies continue into their mutated, toxin resistant genes. Refer to this LiveScience.com link for the related article
Current science believes that the Universe began about 13.7 billion years ago. The earth came to existence about 4.5 billion years ago, with the first basic forms of life starting a mere 3.8 billion years ago. Our friends the humble fish appeared about 500 million years ago and mammals only 65 million years ago. Here’s a visual timeline of evolution I found.
