Extinction and De-Extinction Efforts: A Look at Past and Present

Extinction refers to the complete annihilation of a species, which is marked by the death of the last surviving member of that species. In 1796, Georges Cuvier, a French naturalist, provided compelling evidence that proved extinction to be a factual phenomenon. It is estimated that over 99 percent of all species that have ever existed on Earth are currently extinct. The fossil record indicates that there have been five major extinction events in the past 500 million years, with the most recent event occurring during the Cretaceous period 65 million years ago. This event resulted in the extinction of more than half of all marine species and many families of terrestrial plants and animals. It is believed that an asteroid or comet caused this extinction event. In more recent times, human activities such as overexploitation of natural resources, hunting and fishing, habitat destruction, and pollution have caused extinctions. Other causes include climatic changes, genetic factors, invasive species, and disease.

The Pyrenean ibex illustration was featured in the book "Wild Oxen, Sheep & Goats of All Lands: Living and Extinct" (1898) authored by Richard Lydekker, an English naturalist who lived from 1849 to 1915

Examples of species that have gone extinct in recent times include the woolly mammoth, the passenger pigeon, the Tasmanian tiger, and the Pyrenean or Spanish ibex. However, not all scientists agree that "extinct is forever," and there have been attempts to revive extinct species through deextinction efforts. The most commonly proposed method involves cloning, which was popularized in novels such as John Brosnan's Carnosaur (1984) and Michael Crichton's Jurassic Park (1990). In this process, a viable DNA sample is taken from an extinct species that has been gone for no more than thousands of years, and the DNA is gestated in a host animal.

Although limited success has been achieved in de-extinction efforts so far, there is renewed interest in the field. In 2003, Spanish researchers attempted to clone a Pyrenean ibex using frozen tissue obtained from the last living member of the species, but the attempt was unsuccessful. In 2009, an ibex clone was born alive but died seven minutes later due to an unrelated respiratory ailment. In 2013, there was active discussion and debate surrounding deextinction, and Russian and South Korean scientists announced plans to clone a woolly mammoth from well-preserved remains found in Siberia.