Jump to ratings and reviews
Rate this book

I Used to Be a Fish

Rate this book
From debut author-illustrator Tom Sullivan comes a surprising and innovative picture book that is both a light introduction to the science of evolution and a tribute to every child’s power to dream big.

In I Used to be a Fish, a boy is inspired by a pet fish and fueled by imagination to tell a whimsical version of his own life story, which mirrors the process of human evolution. Children—and adults—will love the Seussian absurdity of this tale.

The book features a timeline of life on earth and an author’s note, which includes important facts about evolution.

48 pages, Hardcover

First published October 11, 2016

77 people want to read

About the author

Tom Sullivan

6 books7 followers
Tom Sullivan is an author, illustrator, and graphic designer based in Boston, Massachusetts. He studied at the New England Institute of Art where he earned a Bachelor's degree in Graphic Design.

After spending the first ten years of his career as a freelance Art Director and Designer, Tom switched gears to pursue his love of storytelling. He is the author and illustrator of the Balzer + Bray/HarperCollins picture books I Used To Be A Fish, BLUE vs. YELLOW, Out There and the graphic novel series Unsolved Case Files.

Ratings & Reviews

What do you think?
Rate this book

Friends & Following

Create a free account to discover what your friends think of this book!

Community Reviews

5 stars
61 (20%)
4 stars
87 (28%)
3 stars
100 (33%)
2 stars
43 (14%)
1 star
12 (3%)
Displaying 1 - 30 of 86 reviews
Profile Image for Miss Ryoko.
2,684 reviews172 followers
May 22, 2017
A picture book about evolution. I like that this book exists, and I also like the fact that Tom Sullivan put some facts about evolution in the back. While I'm not going to complain about this book, we all know there are lots of people out there who will, so I appreciated the fact he put some concrete evidence that doesn't contradict or deny anyone else's opinions or beliefs.

The facts are this... evolution DOES exist whether you want to believe that we as humans evolved from early life forms or not. You can still believe a higher being created the world and agree the evolution exists. We've seen it so many times in species and on our planet that species change and adapt to survive. Even human beings have in our lifetime. So I can appreciate that Sullivan essentially brought up that point with his facts.
Profile Image for Jennifer.
143 reviews14 followers
December 27, 2016
The day when you read an adorable and accessible picture book about evolution for very young kids and it's written in consultation with the National Center for Science Education? Is a very good day.
Profile Image for Brian.
27 reviews
May 24, 2020
The boy who is telling this story is a liar. Some examples:

1. If this kid used to be a fish... 530 million years ago... he would be dead by now, not constantly evolving and changing through the hundreds of millions of years. He would have been dead a LONG time ago and not around today to tell this story. No kid is over 530 million years old. You stop being a kid when you turn 11-17. Rubbish.

2. Evolution, if there is such a thing, isn't predicated on the premise of "getting tired" and therefore growing some legs. Or growing fur to avoid predators. Evolution is the process of generations of things going wrong and the beings with the non-beneficial wrong things dying. The beneficial wrong things help individuals keep species alive. That is evolution.

3. The picture of the naked person who "lost all my fur" clearly has hair on his head, a beard, and small tufts of hair growing out from all over his skin. He didn't lose all of his fur. This is an exaggeration, which, though technically not a lie, is still NOT TRUE.

4. THIS ISN'T WHAT JESUS SAID HAPPENED!

Apart from the... inaccuracies... made by this child there are some underlying theoretical and metaphysical issues with the premise of the text.

1. There is no mention whatsoever of the sub-prime mortgage crisis and how it would have impacted his move from a hut to a house. Hut-dwellings are typically indicative of a low-credit score, nomadic society.

2. We go from cave drawings and hieroglyphs up to 20,000 years ago to rather glibly, "oh, I build a bunch of houses now" in the span of three pages. There is so much unique human history that was overlooked in this span of time. For example:
a. The first human sacrifices to various gods and goddesses in order to make it rain / not rain anymore / rain at a different time.
b. The first person who figured out that in order to make tequila you needed to BOIL A CACTUS FOR 3 DAYS!
c. The genius who decided to make a margarita for the first time.
c. The most recent Ice Age?
d. The only three times the Chicago Cubs will ever win the World Series. Ever.

3. Obviously flying isn't going to be the next evolutionary trait that we humans encounter. We seem, as a species, to be on a... downward trajectory... overall. We have tantrums because we're recommended to wear masks in public to help keep other people safe but we couch it in some theoretical fight to maintain our freedoms and our "rights" instead. Obviously, the next evolutionary step up for us has to be growing a third arm. It's the only thing that makes sense.
Profile Image for Erin.
2,684 reviews
August 12, 2020
I like the concept of a picture book about evolution that is presented in a simple way for kids, but this one is way too simplified. It is washed down so much that the real concept is lost. Saying “I used to be a fish” makes it sound like the one organism itself changes through history. Kids are certainly able to understand the concept of offspring. I would have preferred if the first fish told of its children growing feet and then their children growing fur, and so on. This is still too simple because it leaves out all the millions of years between the stages, but at least it doesn’t give the impression of metamorphosis. The author’s note helps to clear this up, but that page is very text heavy and, for the intended reader (age 4-8), would require a grown-up’s help in understanding.
24 reviews
April 14, 2025
This fun and silly book follows a character who says he “used to be a fish,” showing how living things change over time. With bright pictures and simple words, it’s a great way to help kids understand evolution. It’s funny, easy to follow, and a great conversation starter about science and how we’ve all changed through history! I liked how at the end of the book, the last page showed "A brief history of life on Earth" with a small timeline about how things (more specifically animals and humans) evolved. I can see myself using this in a classroom to introduce the science concept of life!
Profile Image for Kelly.
1,059 reviews36 followers
May 26, 2017
A picture book that presents a simple rendition of a child's interpretation or perhaps wish of evolution. Bright, clean and simple colors will grab the attention of really young readers and present the basic facts with a nice illustrated timeline at the end. In the end this book can be looked at through the lens of following a character through a journey of his imagination or as a small stepping stone to introduce the topic to small children.
Profile Image for Brittany.
2,653 reviews4 followers
December 24, 2017
I picked this one up thinking it was really cute and like a Jon Klassen book. Boy was I wrong! This book is about evolution. The fish "used" to be a fish and then went through all the changes to become a human. This was targeted to the wrong audience. Kids won't understand this. It is a picture book geared for ages 4-8. So, in short, if you aren't pro-evolution, skip this one. If you want a good simple book to teach evolution, this is the one for you.
Profile Image for Kris Dersch.
2,371 reviews24 followers
April 24, 2018
I found this one kind of annoying. I like the idea of a picture book on evolution, but to me there wasn't enough information to call it a good nonfiction book or enough story to make a good picture book. It's definitely a fictionalization of the topic and pretty oversimplified...I just feel like they could have done better. The kid overruled me, though, he's reading it to himself right now so maybe I'm completely wrong.
Profile Image for I Read, Therefore I Blog.
915 reviews9 followers
September 13, 2020
Tom Sullivan’s self-illustrated picture book is a charming fictionalised take on the subject of human evolution that is perfect for parents seeking to introduce their little ones to the topic. The illustrations have a delightful sense of mischief and whimsy and there’s factual information at the back for adults reading this to children so they can answer any questions and give context to evolution in the context of the history of the planet.
1,393 reviews44 followers
October 2, 2024
Cute intro to evolution of humans from the fish stage. Maybe a little over-simplified though and could lead to an incorrect idea of humans. I also would have liked to have seen a bit about how the various stages of evolution affected us/have lingered in us, e.g. we hiccup because we once had gills.

This was probably my quickest borrow ever - borrowed (since I had ordered it at the library), read it and returned in like 3 minutes.
Profile Image for Vicki.
724 reviews15 followers
December 3, 2016
This is a fun and playful take on evolution. I think it would require a bit of conversation to say that this can't all happen in one creature's lifetime -- if you can give a basic rundown of what evolution is, it's fun to look at the progression. I love the playful ending about what could come next for humans.
Profile Image for Miss Kelly.
810 reviews1 follower
August 14, 2017
Cute book with simple and bold illustrations. It is a picture book that tells a simple story of how evolution occurs. The very back of the book has a brief time line of the "History of Life on Earth." That was very neat and a nice visual. I want to check out the author/illustrator's website next.
www.thomasgsullivan.com
Profile Image for Heidi-Marie.
3,855 reviews88 followers
March 15, 2018
If you believe in this version of evolution, this is a good book for teaching it to kids. With easy text, simple illustrations, and some humor. While I believe in some parts of evolution, I don't quite believe this version. But the book has a place and serves a purpose. And done well in that, too. But not my cup of hot chocolate.
Profile Image for Kris.
3,567 reviews69 followers
October 17, 2018
I love the idea of picture books about evolution, but this one is a bit disjointed. It’s not sure if it’s a picture book or a non-fiction book. The pictures are cute, but it is almost too simplistic. I do love the chart in the back, and this is a nice, light introduction book that could be used well if supplemented.
Profile Image for Jaclyn Preciado.
33 reviews1 follower
January 3, 2019
Super simplified version of evolution accompanied by a fictional story. This book is great because young readers can read it on their own, and it’s easy for young children to understand the concept of evolution. Great way for kids to understand the big picture when teaching evolution! Author’s note contains factual and helpful info. Great timeline in the back.
705 reviews
Read
August 17, 2020
Ok. A picture book for very young children. For some reason I had thought it was tied to the adult nonfiction book Your Inner Fish and expected it to have more information about evolution. Instead, the presentation of one character who evolved over what seemed to be the span of one lifetime only created confusion about how evolution actually works.
Profile Image for Lillian Slater.
958 reviews
February 18, 2022
A child friendly version of evolution. Not really sure what I was expecting when I picked this book out but this wasn’t it haha. I have to say that the information was laid out in an almost too simplistic approach and I think it would wind up confusing kids or making them think they can fly rather than actually explaining the concepts they were trying to get across.
Profile Image for Jillian.
2,525 reviews32 followers
November 13, 2016
A simple (maybe oversimplified?) look at evolution, probably for small kids...though the Very Small Ones are maybe too literal to grasp that it's not just one kid who went through all these steps. I like the big, easy to follow illustrations.
Profile Image for Jennifer.
730 reviews
February 10, 2017
This is a fantastic story for introducing evolution to children. My son was fascinated with how animals have changed over time and how "young" we are in comparison to the Earth. He is excited by the idea that we are still changing!
Profile Image for Miss Lou.
118 reviews
February 7, 2018
Another that captivates my one-year-old (and husband) from start to finish. He even loves pointing at the timeline at the end. Bold and bright. A first exposure to evolution. A picturebook for all ages.
Profile Image for Phyll.
99 reviews1 follower
June 30, 2018
I liked the rhyming elements and the simple/clear illustrations but it's too overly simplified for me and I don't like the conflation of biological evolution and the more colloquial sense of the term. May revisit.
Profile Image for Meredith.
4,142 reviews73 followers
May 17, 2020
This picture book explains human evolution.

A timeline of life on earth is included at the back, and the definition of evolution as well as some facts are given in the author’s note.

I’m rather surprised this title hasn’t shown up on the banned books lists.
369 reviews4 followers
November 16, 2020
This is a cute book with cute pictures. It is a very simplified version of evolution, if you believe that you came from a fish and evolved eventually into a human.

The pictures are cute--especially when he evolves from a hairy ape like man to a man with a beard who is naked!

Profile Image for Paula Hollohan.
510 reviews
November 23, 2016
Covers evolution by personalizing it with line drawings and one character. Not sure the audience will understand the big picture nature of this book. K-3.
Profile Image for Katie.
1,278 reviews11 followers
June 15, 2017
Simplified story of the evolution of humans.
Three colors. Big text - could be used as Beginner Reader.
Displaying 1 - 30 of 86 reviews

Can't find what you're looking for?

Get help and learn more about the design.