Dr. Universe explains our fingers and toes

Ask Dr. Universe is a science-education column from Washington State University.

  • Thursday, December 20, 2018 1:33pm
  • Life
Illustrations by Rob McClurkan

Illustrations by Rob McClurkan

Dr. Universe: Why do we have five fingers and five toes? -Eli, 11, Edinburgh, Indiana

Dear Eli,

While humans may be one of the few animals that can give a high five, they are one of many with five fingers and toes.

Humans are part of the primate family, which also includes monkeys, apes, and even lemurs. As a member of the family, you also have fingernails instead of claws and pads on your fingertips that help with your sense of touch.

We actually see a total of ten fingers and toes in a lot of other vertebrates – animals with backbones. Fossil evidence of some early vertebrates show that some creatures had six, seven, or even eight fingers. That’s what I found out from my friend Sian Ritchie, who teaches biology at Washington State University.

Ritchie told me how animals tend to keep the characteristics or traits that help them survive in an environment. These are called adaptations. They may also over time lose some traits, like a finger or two.

While it’s clear that five is a common number, the truth is we don’t entirely know why it is so common. When we look at animals with five digits we do see some other patterns, including more sophisticated wrist and ankle bones. Those more complex wrists can help animals when they use tools, while ankles can help with things like walking, climbing and balance.

Meanwhile, some animals are actually born with an extra toe or finger. Like most cats, I have five toes on my front paws and four toes on the back paws. My toes help me balance, climb trees, and go on lots of adventures. It turns out there is actually a place in Florida where you can find dozens of six-toed cats.

The writer Ernest Hemmingway lived there and he had a cat with six toes. When that cat had kittens, it passed down information through genes. Genes are the kind of the blueprint that tell us how to develop. Ritchie adds that Hox genes, in particular, carry a lot of the instructions for humans to develop different parts, including fingers and toes. Our genes help determine our hair color, eye color, and even whether we will be born with a total of ten toes and fingers.

When you were growing in the womb, your fingers and toes were actually kind of webbed. But as time passed, you started to form bone and more defined digits. Believe it or not, when horses are developing in the womb, they also carry some of the genetic instructions for five digits. The ancestors of horses used to have five toes, but they’ve adapted to have only one.

We also find finger bones that are sort of hidden in different animals. If we looked inside the wings of a bat, we would find five fingers. If we took an x-ray of a whale’s fin, we would find five finger bones inside their flippers. Why do you think that might be? Send me your ideas sometime at Dr.Universe@wsu.edu.

Sincerely,

Dr. Universe


Talk to us

Please share your story tips by emailing editor@rentonreporter.com.

To share your opinion for publication, submit a letter through our website https://www.rentonreporter.com/submit-letter/. Include your name, address and daytime phone number. (We’ll only publish your name and hometown.) Please keep letters to 300 words or less.

More in Life

Boeing announces $700,000 in grants for West Coast wildfire relief

Washington’s Northwest Harvest food bank will receive $100,000

A COVID-19 test kit
Local COVID-19 research study now available in Spanish, seeking volunteers

The study is for adults with high risk of exposure to COVID-19

Diya Garg, left, distributes Mighty Crayon recycles crayons and coloring books for Seattle students. Courtesy photo/Diya Garg.
Getting crayons to kids runs in the family

Eastside nonprofit Mighty Crayon is relaunched by younger sister of founder, repurposing used restaurant crayons

Renton moms turn to YouTube during pandemic

Renton Kreations also uses the platform for kids to present book reviews

2020 Honda CR-V Hybrid. Courtesy photo
2020 Honda CR-V Hybrid | Car review

There’s a reason Honda’s CR-V has been America’s top-selling crossover vehicle over… Continue reading

2020 Ford Ranger SuperCrew Lariat. Courtesy photo
2020 Ford Ranger SuperCrew Lariat | Car review

Ford’s venerable compact Ranger pickup went away for a while. But it… Continue reading

Renton church offers online funeral services

As a result of COVID-19 closures, the church decided to find a way for people to gather and mourn loved ones

Washington State Fair cancelled

COVID-19 outbreak claims another event

Founder and co-owner of Red Tea Room Donna Wong puts the finishing touch on their most popular dessert— Lemon Meringue Glacée. Photo by Haley Ausbun.
Renton catering company pivots during pandemic

The Red Tea Room Catering’s move to takeout helped keep the company going— and get closer to neighbors

Courtesy of Lindbergh High School.
Congrats to the Class of 2020— virtual ceremony June 15

Students were also celebrated using walk-up ceremonies at Renton High School, Lindbergh High School, Hazen High School and Talley Sr. High School

TLG Motion Pictures CEO Erik Bernard and TLG founder Courtney LeMarco on a set. Photo courtesy TLG Motion Pictures.
Local production company seeking film, TV pitches from young minority creatives

The Big Pitch competition, put on by TLG Motion Pictures (“Hoarders”), started about six months ago.

Relay for Life of South King County moves online

American Cancer Society donations to be taken during May 30 virtual gathering