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  • Writer's pictureSTEM Today
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Why Do Most Mammals Have Five Fingers?

May 2024

Researcher: Sakina Shaikh Mohammed

Editor: Neha Chowdhury


Living organisms have been around the world for millions of years. Many living organisms have evolved, considering the famous example of “human evolution theory." A key part of the body that has significantly evolved or developed is the fingers.


Fingers are a vital key in the body of tetrapods (vertebrates (mammals with a backbone) with four limbs). Helping us feel the environment and objects around us and carrying out our daily tasks, such as brushing our teeth, riding a bicycle, taking down our notes, etc. For a long time, that is, over 340 million years ago, tetrapods have had five fingers, excluding the cases of polydactyly (a condition when a human has more than five fingers) and oligodactyly (a condition when a human has less than five fingers). But how did this change occur? Why do most mammals have five fingers or digits?


Let’s start with the first question on how tetrapods' fingers went from having six or more fingers to five! It has been stated by Thomas Stewart that this evolution can be related to the trait “homology—a likeness often due to a common origin or, in this case, a common ancestor." This trait has been passed down and is found in almost all the tetrapods. Another theory called ‘canalization’ is the idea that a gene (in this case, having five fingers) becomes more stable and less likely to change when it is passed down from one generation to another.


Another concept is the Hox genes; they determine the basic structure and how the parts of our body should be placed, which take place during early embryonic development. The first hox gene would be your head, then your neck, shoulders, and so on. The development of our five fingers is directly related to the concept of Hox genes. Our oldest ancestors had more than five fingers. Through evolution, these Hox genes came to 5 fingers, since they offer good balance and flexibility and overall help with the daily functions of most mammals.


In contrast, mammals such as pandas have 5 fingers with a modified 6th thumb to help grasp their bamboo, horses (one toe to help them run with stability and support), and whales (one flipper on the outside but with 5 digits in their skeleton). The general reason for the different numbers of toes and fingers is that mammals and any living organism adapt to their environment and lifestyles.


Now that we have our academic answer to the question, “Why five fingers and neither more nor less?” Let's take a look at the different perspectives that people and scientists have. It has been argued over the past few years that having a sixth finger would help humans in their daily lives. As LiveScience.com stated in its article, “Having a sixth finger might help us to have a better grip, type faster, and even play the piano easily too.” Some suggest that having a 6th finger wouldn’t change anything, whereas others believe it will have an impact, especially in the mathematical and counting worlds. Since the number 10 has become a natural base in our counting system, when we have 12 fingers (6 on each hand), the natural base will turn into 12. So, 10, 100, and 1000 will not be our bases; it would be 12, 102, and 1002. Just imagine that!






References

 

This article features images from Pixabay and Canva








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