TL;DR: the sixth mass extinction is just happening due to the human being activities.
The extinction and emergence of species are two side of the same coin, the natural selection. It may take several thousands years for a loser to fade out without our awareness, aka “background extinction”.
There are five mass extinction event during the Phanerozoic(显生宙), and it seems the following homo sapiens activities accelerates the widespread species extinctions:
- Overexploitation, e.g: great auk, dodo etc.
- Ocean acidification. The massive carbon dioxide lower the pH value of the ocean, and make the calcification much harder. The coral will become extinct at the end of the century.
- Global warming: the global warming impacts a threat not only to cold-loving species, but also to the tropical lives. The tropic specifies are extremely specialized for the resource competition, which make them vulnerable for the fluctuate the environmental change.
- Habitat fragmentation. The habitat fragmentation leads to local extinct, then regional, and global eventually.
- Invasive species. The global transportation makes the continents a New Pangaea. Without the evolutionary arms race, the foreign species could be 100% lethal to the local species.
- Cretaceous–Paleogene (K-Pg) extinction event
- Triassic–Jurassic (Tr-J) extinction event
- Permian–Triassic (P-Tr) extinction event
- Late Devonian (Late D) extinction
- Ordovician–Silurian (O-S) extinction events
“leak replacement”: the modern human had sex with the Neanderthals before “replacing” them, thus the modern human has 1 - 4% Neanderthals’ DNA.
Groups of amphibians may genetically speaking be as different from one another as, say, bats are from horses.
The author uses the experiment in Castello Aragonese to show a warning sign of ocean acidification.
The scientist inspect the iridium mass in the clay to propose the mass extinct is caused by the asteroid impact.