Saltation, as proposed by Hugo de Vries, is a theory of evolution that suggests rapid and significant evolutionary change can occur through sudden, large-scale mutations. In this theory, de Vries proposed that new species could arise abruptly from such mutations, rather than through gradual accumulation of small changes over time, as suggested by Charles Darwin's theory of natural selection. These sudden mutations, according to de Vries, could result in the appearance of entirely new characteristics or traits in an organism, leading to the emergence of distinct species. This concept of saltation contrasts with the gradualism proposed by Darwin, where evolutionary change occurs slowly and continuously through the accumulation of small variations over generations.

The discovery of the coelacanth in 1938 off the coast of South Africa was highly significant in the evolutionary history of vertebrates for several reasons:

1. Living Fossil: The coelacanth is often referred to as a "living fossil" because it was thought to have gone extinct around 66 million years ago, during the Late Cretaceous period. Its discovery alive challenged the long-standing assumption that coelacanths were extinct, providing a remarkable example of a species that has survived virtually unchanged for millions of years. This sheds light on the evolutionary history and persistence of certain lineages over vast stretches of geological time.

2. Transitional Fossil: Coelacanths belong to a group of lobe-finned fishes called Sarcopterygii, which are considered to be the closest living relatives of tetrapods, the group that includes amphibians, reptiles, birds, and mammals. As such, coelacanths offer valuable insights into the evolutionary transition from aquatic fish-like ancestors to terrestrial tetrapods. Their anatomical features, such as robust limb-like fins and a unique hinge-like structure in the skull, provide clues about the evolutionary adaptations that occurred during this transition.

3. Evolutionary Conservation: The discovery of the coelacanth highlighted the importance of studying "living fossils" and other ancient lineages to understand evolutionary processes, biodiversity, and conservation. Coelacanths are considered a flagship species for marine conservation efforts, as they inhabit deep-sea environments and are vulnerable to threats such as habitat destruction, pollution, and overfishing.

Overall, the discovery of the coelacanth in 1938 was a landmark event in evolutionary biology, reshaping our understanding of vertebrate evolution and highlighting the significance of studying both extant and extinct species to unravel the complexities of life's evolutionary history.

The common ancestor of the great apes (including chimpanzees, gorillas, orangutans, and bonobos) and humans is believed to be a species of hominid that lived millions of years ago. This common ancestor is thought to have existed in Africa, and while its specific identity remains uncertain, it is typically referred to as a member of the hominin lineage. Hominins are a group of primates that includes modern humans and their extinct relatives, such as Australopithecus and various species of the genusHomo. The exact species that represents the common ancestor of great apes and humans is a subject of ongoing research and debate in the field of paleoanthropology.

Hugo de Vries' mutation theory and Charles Darwin's theory of natural selection are both significant concepts in evolutionary biology, but they differ in their mechanisms and explanations for how species evolve:

1. Mutation Theory by Hugo de Vries:

   • Hugo de Vries proposed the mutation theory as an alternative mechanism for evolution.
   • According to de Vries, evolution occurs through sudden, large-scale mutations or "saltations" that produce significant changes in organisms.
   • He suggested that these mutations provide the raw material for evolutionary change, leading to the emergence of new species in a relatively short period.
   • De Vries' mutation theory implied that evolutionary changes could occur rapidly and discontinuously, rather than gradually as proposed by Darwin's theory.

2. Darwin's Theory of Natural Selection:

   • Charles Darwin's theory of natural selection is based on the idea of gradual change over time.
   • According to Darwin, evolution occurs through the process of natural selection, where individuals with advantageous traits are more likely to survive and reproduce, passing on those traits to their offspring.
   • Over successive generations, favorable traits become more common in a population, leading to gradual changes in the species.
   • Darwin's theory emphasizes the role of variation within populations and the differential survival and reproduction of individuals with certain traits in shaping evolutionary change.

In summary, the main difference between de Vries' mutation theory and Darwin's theory of natural selection lies in their proposed mechanisms of evolution. De Vries emphasized the importance of sudden mutations as the driving force of evolutionary change, while Darwin focused on gradual adaptation through natural selection acting on existing variation within populations.