Bats have been around for 50-60 millions year, but there has been a debate between scientists on how they evolved. New evidence has come to light recently that sheds more light on their evolution, so I wanted to write about this here.
Scientists in 2008 found a fossil dated to be over 52 million years old. Research shows that this bat had evolved to fly before it could echolocate.
Evidence of the physical appearance of early bat fossils indicates that bats have always been able to fly. Recently a team of paleontologists stumbled upon the remains of an ancient giant bat (Mystacina miocenalis) in New Zealand’s South Island.
Analysis of this fossil suggests the huge bat roamed the area at least 16 million years ago.
They concluded that based on its limb shape, the bat spent a large amount of time walking on the ground rather than flying. This bat’s two modern relatives also spend part of their lives on the forest floor, scouring for insects.
Did Bats Evolve Twice?
A suggestion has been made whether bats share a common ancestor with humans and other primates. Until recently, evidence to support this theory was almost non-existent. However, biologists in Germany have proven a link using immunological methods.
Immunology refers to studying the immune system and is a crucial branch of medical and biological sciences. The immune system protects organisms from infection through various lines of defense against disease.
The largely accepted view is that bats are a strict mammalian order, Chiroptera, divided into two subcategories. Flying foxes, one of the largest bat species, and fruit bats are combined within the Megachiroptera family. In contrast, the smaller, insect-eating bats and vampire bats are placed in Microchiroptera or microbats.
Microbats are known as insectivorous bats, true bats, or echolocation bats. Most eat insects, while larger microbats also hunt lizards, frogs, and even small birds.
Megabats, also known as Megachiroptera, comprise flying foxes and fruit bats. These bats do not eat insects but feast on nectar and fruits.
They have hard, sharp teeth that let them bite through tough fruit skins. Some bats drink the juice of the fruit while others snack on the fruit. Horseshoe bats are genetically more closely related to the families of fruit bats.
Some scientists now believe that echolocation was used by a common ancestor of all the bats that exist in the world today. Echolocation might have been lost in megabats, only to reappear in a few of these species later, including greater horseshoe bats and lesser horseshoe bats.
Zoologists commonly believe that this categorizing reflects the evolution of all bats from a common ancestral organism.
Are Bats Primates?
Newer studies have shown that these megabats are a primate type, mirroring several characteristics with humans and apes.
Scientists at the University of Heidelberg have looked at the proteins in the blood serum of megabats and primates, which shows enough in common to suggest a close taxonomic relationship between the two groups.
When Did Bats Evolve?
The oldest fossilized remains of bats were dated to be from 50-60 million years ago. Fossils show that even in the early Eocene, their appearance hasn’t changed much up until today.
Predating humanity’s ancestors when they resembled apes, microbats found today were already flying and using echolocation.
Bats are the only mammals capable of flying, but how this ability evolved is uncertain because of a lack of fossilized evidence. The missing link between non-flying mammals and bats has still not been found. Without this connecting species, it is impossible to know for sure the ancestor of modern bats.
Scientists have three separate theories for how echolocation evolved. The first is that bats started to fly before they used echolocation. The second is that echolocation evolved before flight, and the third is that both happened simultaneously. The new pair of fossils dated from around 52 million years ago resolve the issue.
How Did Bats Evolve?
Biologists have debated about how bats evolved because there were no specimens to answer this issue. Finally, fossils were found that could give an answer.
The Royal Ontario Museum in Toronto confirms that flight evolved first, and echolocation has evolved later.
Scientists believe that the Microchiroptera likely evolved from small gliding mammals of the order Insectivora. This order today includes small rodent-like mammals that feed on insects, including shrews and moles.
Scientists believe these bats may have developed the ability to fly for two reasons; to escape predation or to pursue an abundant, diverse supply of flying insects that were evolving at the same time.
If the German biologists are correct, flying mammals arose twice during the course of evolution. The similarities between the two kinds of bats reflect adaptations to their way of life rather than common ancestry. The German researchers are careful to point out that their data does not prove this theory but is compatible with it.
An alternative explanation is that the microbats have evolved more rapidly. This could be the reason why they now appear to differ considerably from the megabats. The bat controversy seems set to continue for some time before being resolved.
How Did Bats Evolve Echolocation?
A bat will fly through the air to catch insects or eat fruit. They can also hunt prey by producing a high-pitched sound before listening for the echo to return.
The Journal of Nature Letters recently published a study that shows that the genome regions responsible for echolocation are strikingly similar between bats and dolphins.
The earliest known complete bats from the Eocene were already capable of flight and echolocation. In the absence of direct fossil evidence, there have been many scenarios to explain echolocation evolution.
Theories assuming chiropteran monophyly have presumed that the pre-bat was nocturnal, lived in trees and ate insects. Following this assumption, the hypothesis can be divided into three categories.
Echolocation evolved first, flight evolved first, or a tandem development of flight and echolocation. All three theories assume that flight evolved only once in the lineage. In contrast, the chiropteran diphyly hypothesis suggests that flight evolved twice throughout history.
If they developed with hands, a bat would not have sufficient membranes to descend and glide. The development of these membranes provided propulsion if flapped.
Flapping is not an option for some other mammals, and this is where confusion as to the bat’s origins comes in. An Asian mammal, the colugo, with its extended proximal membranes and small hands, can glide and does so with ease.
The African palm civet has no gliding membranes whatsoever, but it has been observed free-falling from trees over and over in a spread-eagle configuration, apparently in play. This maneuver also helps them to avoid aerial and tree-dwelling predators, such as birds and snakes.
Did Bats Evolve From Rats?
Most evolutionary scientists agree that bats must have evolved from mammals. However, there isn’t enough hard evidence as to which ancestor today’s bats evolved from.
Scientists now theorize that bats, the only mammal known to have developed flight, evolved from small rodent-like animals, including animals such as rats.
A discovery in 2008 did fill in a piece of this evolutionary puzzle with an exciting find. The oldest fossilized bat was dated to be over 52 million years old. This fossil was used to put to rest a long-standing argument in the scientific community.
The research found that this animal was able to fly but did not have the use of echolocation. The American Museum of Natural History in New York declares, “It’s notably a bat, but different to any previously known. In many respects, it is a missing link between bats and their non-flying ancestors.”