Bats have been around for a long time, but there has always been a debate between scientists on how they evolved. New evidence has come to light recently that sheds light on the evolution of bats, and I wanted to write about this here.
Scientists have found fossils offering them insight as to how long bats have existed. A fossil found in 2008 was dated to be over 52 million years old. Research shows that this bat had evolved to fly before they 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 an ancient giant bat (Mystacina miocenalis) in New Zealand’s South Island.
Analysis of the bat fossil suggests the huge bat roamed the area at least 16 million years ago.
They concluded that based on the shape of its limb bones, the bat spent part of the time walking on the ground, rather than flying. The bat’s two modern relatives also spend part of their lives on the forest floor, scouring for insects.
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Did Bats Evolve Twice?
A suggestion had been made before, as to whether bats share a common ancestor with humans and other primates. Until recently, supporting evidence was almost non-existent. However, biologists in Germany have proven a link using immunological methods.
Immunology refers to the study of 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 accepted view is that bats are a strict mammalian order, Chiroptera, which are divided into two subcategories. Flying foxes, one of the largest species of bat, and large fruit bats are combined within the Megachiroptera family while the others, small insect-eating bats and vampire bats, are placed in the family of Microchiroptera.
Microbats are also known as insectivorous bats, true bats or echolocation bats. Some microbats do not eat insects; however, most do consume insects for food. Larger species of microbats hunt lizards, frogs, and even small birds.
Megabats, also known as Megachiroptera, are also referred to as flying foxes or 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. The horseshoe bat eats insects and tends to be small bats are genetically more closely related to the families of fruit bats.
Some scientists now also believe that echolocation was used by a common ancestor of all the bats that exist in the world today. Echolocation might have then 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.
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Are Bats Primates?
Despite this, newer studies have shown that these megabats are a type of primate, mirroring a number of 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 found fossilized remains of bats were dated to be from 50-60 million years ago. The fossils show that even in the early Eocene, the appearance of bats hasn’t changed much up until today.
Predating humanity’s ancestors when they resembled apes, bat species similar to species of the microbats found today were flying and using echolocation for hunting insects.
Bats are the only known mammals capable of flight. How this ability evolved, or from where is uncertain because of a lack of fossilized evidence. The missing link between non-flying mammals and bats has still not been found and is important to provide an explanation. Without this connecting species, it is impossible to know for sure the ancestor of modern bats.
Scientists have conflicting opinions of three separate theories for echolocation. These are that the bats started to fly before they used echolocation; echolocation came before flight or both happened simultaneously. The new pair of fossils dated from around 52 million years ago resolve the issue.
How Did Bats Evolve?
Biologists have hotly debated about how bats evolved because there were not any specimens to answer this issue. Finally, a combination of features witnessed in this species gives us an answer at last.
The Royal Ontario Museum in Toronto confirms that flight evolved first and echolocation must have 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 such as shrews or moles.
Scientists believe these bats may have developed the ability to fly for two reasons; to escape predation or to pursue an increasingly abundant and diverse supply of flying insects that were evolving at the same time.
If the German biologists are correct, it means that flying mammals arose twice during the course of evolution and that the similarities between the two kinds of bats reflect adaptations to their way of life rather than to common ancestry.
The German researchers are careful to point out that their data does not prove this theory but that they are 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 with its membranous wings to catch insects or eat fruit. But they can also hunt prey by producing a high-pitched sound and then listen for the echo to return.
The Journal of Nature Letters recently published a study. The study shows that the regions of the genome 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 concocted scenarios to explain the evolution of these behaviors and their distributions in bats.
Theories assuming chiropteran monophyly have generally 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 of these theories assume that flight evolved only once in the lineage. In contrast, the chiropteran diphyly hypothesis suggests that flight evolved twice throughout history.
Developed with hands, a bat would not have sufficient membranes to descend and glide. The development of these membranes could provide 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 only 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 evolution scientists agree that bats must have evolved from mammals. However, there isn’t enough hard evidence as to which common ancestor, today’s bats evolved.
Scientists now theorize that bats, the only mammal known to have developed flight, evolved from small rodent-like animals, which now include 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.
Did flight, or echolocation, the bat’s flight system, develop at the same or different times.
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.”
You may be suprised to know that bats exist in Alaska. I have written an article on this, which you can find here.