INCREDIBLE NATURE : SIMILARITIES AND DISSIMILARITIES OF KOALAS AND HUMAN FINGER

Apes and other primates are well known to have human-like dermatoglyphic patterns on the hands and feet. A study had been done on bare areas of skin on digits, palms, and soles of a 46yrs old female chimpanzee and an adult male koala using the standard ink printing and scanning electron microscopy. The ridges of digits, palms, and soles were found to be similar in size and density to humans. Koala skin is found to be covered either by papillary ridges of the size, shape, and arrangements very similar to humans or by warts- islets of dermal papilla separated by grooves. On the hands and feet of the Koala, the presence of whorls, arches, and loops have been observed just like human patterns Whorls and loops are found to be surrounded by tri radii similar to those observed in humans. Not only that, but they also have fingerprints that are so human-like, that crime scene investigators have actually got them confused. Koalas feeding habit is directly related to the evolution of fingerprints on their hands and feet. Their feeding habit includes climbing vertically on the particular branches of eucalyptus trees and having a handful of leaves into their mouth. So, the development of fingerprints can be best explained as a biomechanical adaptation to grasping, which produces non-unidirectional mechanical effects on skin. Only small portions of koala fingertips are covered by ridges, the majority of the tactile skin being covered by warts.

According to study two hypothesis were considered between humans and species which areas follows-

1. Dermatoglyphic similarities, due to the high heritability of dermatoglyphic patterns, are an expression of genetic similarities, 

2.Dermatoglyphic similarities, due to dermatoglyphic pattern configuration is dependent on the morphology of underlying structures are an expression of functional, biomechanical similarities 

But later on, the  first hypothesis was considered inappropriate as compared to second.

• According to another study, most of the skin on palms and soles of koalas is covered by warts, ridges.
• However, warts also show a discernible linear organization. Certain dermatoglyphic patterns such as arches, loops, triradii, and possibly whorls are being displayed by ridges or linear streams off warts.
• In different individuals, warts, and ridges are intermixed and covers different proportions of skin. Warts like interrupted skin ridges are also found in humans.
• According to the study parallel ridges cover the entire fingerprints of koalas.
• Whilst the remainder of the skin covered by warts
• On every digit of humans, Arch pattern was commonly seen, while tips of pedal digits were found to be covered simply by ridges perpendicular to the long axis of a digit with the exception of the first one where an arch is drawn
• No comment was done on the presence of human-like dermal ridges but simply noted the apical pads are present and striated
• Presence of ridges and warts on the digit, palms and soles of koalas were seen to be logical because koalas spend most of their lives climbing trees as the fud on foliage and dermal ridges enhanced the skin friction
• But this fact of friction increased hypothesis was refuted because in most arboreal marsupials apical pad ridges were present, run mostly parallel to digit axis and such axially oriented ridges cannot oppose the backward thrust of the digits in locomotion.
• Marsupials maybe an example of independent evolution of the same skin adaptation to climbing and the presence of dermatoglyphic patterns very similar to human ones.
• However, primitive mammalian characteristics of the ridged tactile skin covered with the dermatoglyphic pattern consistent with the 3d configuration of underlying pads that evolved before the spilled between marsupials and placentals occurred.
• Generally it is assumed that the earliest mammals were arboreal.