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.

Leonardo da Vinci: Unearthing the Anatomical Mastery

Leonardo da Vinci, an unquestionable polymath and true genius, also stood as a pioneering human anatomist. His meticulously detailed works, continuously scrutinized for their precision, have received validation through modern imaging techniques. The field of human anatomy had seen scant progress for centuries since Galen, whose limitations included a lack of access to human cadavers. Pre-Leonardo, depictions of the human body were primarily superficial, lacking insight into its internal mechanisms, which were verbally, not visually, explained.

In Leonardo's birthplace of Florence, he gained access to cadavers, embarking on a dissection journey from 1489 onwards. Over two decades, he meticulously dissected some twenty to thirty corpses, ranging from healthy to diseased and deformed. Within his human anatomy notebook, he recorded precise measurements of body proportions, accompanied by multi-view drawings. For instance, his representations of the hand and leg featured intricate layers, showcasing the relationships among arteries, muscles, ligaments, nerves, and bones.

Leonardo's in-depth exploration extended to capturing a wide array of facial expressions, which he skillfully incorporated into his renowned artworks. While celebrated for his accurate depiction of a fetus attached to its umbilical cord, his sketches of the female reproductive system contained some errors, leaning closer to an animal representation than a human one. Beyond drawings and sketches, his thirst for understanding the body's functioning led him to create physical and mechanical models simulating organ operations, such as the opening and closing of heart valves. These models informed his drawings and studies.

Leonardo aspired to create a comprehensive treatise on human anatomy, envisioning its utility for medical practitioners. Unfortunately, his passing in 1519 resulted in these anatomical papers being tucked away among his private possessions. After changing hands multiple times over the years, they resurfaced in the British Royal Collection at the close of the seventeenth century, where they currently reside.

Leonardo created the "Vitruvian Man" around 1490, a pen and ink drawing inspired by the concepts of Vitruvius, a Roman architect from the first century BCE. Vitruvius posited that the perfect human body could be depicted using the geometric shapes of a circle and a square.