Final answer:
Primate identification and classification are hindered by the rarity of fossils, with only 3% found, and the need for precise dating methods. Additionally, the anatomical diversity and evolutionary theories add to the complexity of establishing clear primate lineage.
Step-by-step explanation:
Identifying and classifying primates from the past is complicated by several factors. One major challenge is that fossils are incredibly rare; it is estimated that there have been more than 6,000 primate species, but remains of only about 3 percent have been found. When a fossil is discovered, understanding its context in the primate evolutionary history requires accurate dating. Earlier, only relative dating methods were available, allowing for an approximate age determination in comparison with other fossils. With the advent of absolute dating methods, scientists can now establish a more exact biological age in years.
Moreover, the large brain of primates, their opposable thumbs, and other unique anatomical characteristics like five fingers and various types of teeth provide clues to their lifestyles. However, determining the true lines of descent among hominids remains complex due to incomplete fossil records and the fact that primate evolution has included significant diversification into different ecological niches. Theories such as the arboreal theory, the visual predation hypothesis, and the angiosperm theory have been proposed to explain primate evolution but are still debated among scientists.
The division of Order Primates into prosimians and anthropoids adds another layer of complexity. Prosimians, such as bush babies and lemurs, differ significantly from anthropoids which include monkeys and apes, in terms of their nocturnal habits, brain size, and anatomical features. This diversity across the primate order makes classification based on limited fossil evidence even more challenging.