The Montessori Timeline of Life – Redesigned and Scientifically Accurate

The Montessori Timeline of Life is an iconic material used in the elementary curriculum. Every year, the timeline is presented during the Second Great Lesson. As students get older, the knowledge from years past helps them delve even deeper into all subject areas related to biology, geology and the history of Earth as a whole.

This is a sample of the domains and lessons that would follow from The Coming of Life depending on the readiness of the child:

• Classification of living and nonliving things
• Classification of plants and animals
• Botany: Needs of the plant
• Botany: Parts and function of the plant
• Biology: Animal research projects
• Adaptation and Evolution
• Ecosystems and Biomes
• Paleontology and Geology
• Extinction and extinction events
• Dinosaurs!
• Going out trips to natural history museums, aquariums, or nearby woods/beach

This material is a high leverage investment, so I believe it’s worthwhile to have the best timeline you can. One that students can get more information out of as years go by.

The Rhyme and Reason Timeline of Life Bundle

• The control chart (this is the filled in chart)
• The mute chart (this is the blank chart)
• 95 creature and event cutouts from the control chart including plants, fungi, animals, and events.
• 59 word label cutouts from the control chart.

Why did I remake the timeline?

With my background in science, I found the original timeline difficult to understand, difficult to present and downright baffling in places. Why are jellyfish and trilobites on the same line? Why are modern mushrooms before ferns? What does it mean when a line goes up or down or connects? When I searched online for the timeline I would add to my classroom, I found that some remakes were better than others, but none addressed some of the really fundamental issues I had with the design. Mainly, they didn’t show any meaningful relationships between animals- the foundational concept behind evolution and all life on earth.

Dr. Maria Montessori philosophically disagreed with Darwinian evolution, which I think provides a plausible historical reason for this omission.

I understand that the original Montessori Timeline of Life was meant to be “impressionistic,” which means it is simplified and meant to be imaginative. But I found the original timeline to be well beyond “impressionistic.” I believed that there were so many factual errors and misleading pieces of information, that the only impression a child could make is an incorrect one.

So, I set off to remake the timeline, not really know what I was getting myself into when I started (as most colossal projects begin). I thought I would be able to tweak some of the lines, draw a few dozen creatures and be done in a month or so. No. Not at all. This project took me over nine months, more than the entire school year. But in the end, I’m very happy with the results.

Features of the Rhyme and Reason Timeline of Life

To start with, the Rhyme and Reason Timeline of Life includes the Precambrian Eon. This lets you pick up where the First Great Lesson left off and bring back the impressionistic charts and showing how they fit in with the story. In other words, this timeline starts from the formation of Earth, whereas most other timelines start at the Cambrian Period.

I like to point out to students that this is why there aren’t any plants and animals in chart 5A- they didn’t exist yet!

This timeline is proportional, all of the Phanerozoic Eon is set to the same scale. For the the Precambrian Eon I used a fun trick with the Long Black Strip.

To make the entire timeline scaled exactly the same (every 0.09 inches is 1,000,000 years), it would have needed to be 500(!) inches long, with only the last 60 inches having life in it – boring! So I shrank the first 4 billion years into a mere 18 inches and used a visual of the long black strip scrunched up to make it all right. (If you want your long black strip to be perfectly scaled to this timeline, make it 41.6 ft. I don’t think that’s remotely necessary, but now you know.)

During a follow up lesson, bring out the Long Black Strip and actually scrunch it up against the timeline for a sensorial demonstration.

What Do The Red Lines Mean?

The red lines are a very loose representation of phylogenic common ancestry. Creatures that are on the same line, share a common ancestor and are more closely related to each other than to creatures on other lines.

Where a red line branches off, there has been a significant enough change that we call that lineage of creatures something else (ex. now called amphibians instead of fish). Each red line branch is labelled.

The lines do not represent creatures changing into other creatures. If I were to make the timeline perfectly accurate, every creature would be on its own branched line (with just about all of them ending as soon as I start it), but that would be very cluttered, less clear and it would make the timeline quite “bushy”! in this sense, the timeline is still impressionistic.

Creatures on the same line are more related to each other than creatures on parallel lines, and you can trace the lines backwards to the nearest shared branch to see when they had a common ancestor. This timeline does not tell you what the common ancestor was.

Where Are Creatures Placed?

Some creatures that still exist today have been around for a very long time, some since the Cambrian explosion. When a creature has a long “existence” time, I had permission to place it anywhere on the timeline that it had existed.
Most creatures have a rather short moment in the spotlight, like Pikaia the first fish, but others like the trilobites and snails have a long reign on Earth. Let’s take a look at these three examples:

1. Pikaia lived and died during the Cambrian explosion, that’s where he’s placed and there is nowhere else this little guy could be.
2. The snail is placed in the Quaternary, but it has been around in one form or another since Cambrian. It could have been placed anywhere on the timeline.
3. Trilobites rose to dominate the ocean floors during the Cambrian period and went extinct during the Permian-Triasssic extinction event. I drew nine different trilobites to cover this long period of time.

Pikaia and Trilobites are shown in a very concrete way, with no ambiguity, but many of the creatures are ambiguous, as they are on every timeline.

If I were to draw multiples like I did for the Trilobites for every creature that lived for many eras it would be impractical and cluttered. Given my constraints, I chose to draw and place each creature once.

I hope to clear any confusion with the research cards (not made yet) that accompany the Timeline. The cards will list first known existence to its extinction period. An extension activity for the mute timeline could be to group animals by first existence and then by last existence to see where “hot spots” are for new creatures and extinctions.

A final design note, the name is where the creature is in time, not where the graphic starts or stops. This is especially relevant for creatures that take up a lot of visual space (I’m looking at you cameraoceras).

What Creatures Are On The Timeline of Life?

With the entirety of the tree of life to choose from, it was at times really hard to decide what to include and what had to be excluded. (I was crushed when I had to cut plesiosaurus, my favorite not-technically-a dinosaur).
I tried to keep the spirit of the original and kept the most popular creatures, such as the trilobites and giant dragonflies, but others I had to be omitted, almost always for space reasons. My timeline does not have “sea lilies” (crinoids) or jellyfish, which might be a dealbreaker to some Montessorians, and I get that.

Overwhelmingly, most were selected because of they had evolutionary significance, important fossils or were a transitional species. Animals that would be easy and interesting for students to research was a major consideration and bonus points if the student had a good chance of seeing real fossils in a museum or in the classroom. There is a mix of specific species (like velociraptor, prototaxities, cyanobacteria), which are in italics, and generic groups (like spiders, snails, turtles).

Some were added as personal selections from like-minded Montessorians who helped me remake the Montessori Timeline of Life including the seahorse and mantis shrimp – my personal pick was the chicken!

This brings me to…

The Criminal Sidelining of Fungi

Nearly every commercial Timeline of Life I looked at had no fungi present. Sometimes, if it was on the timeline, it was placed with plants, which is completely unacceptable to me.

On a personal note, I find fungi to be the most fascinating of the kingdoms and I think they’re very accessible to children to learn about. You can take a hike in any wooded area, on any given day and see a vast array of biodiversity in fungi from toadstools to conchs and slimes to jellies.

I took these pictures of fungi during hikes with my students:

From an evolutionary perspective, fungi have played an enormously important role in forming the biosphere and they work symbiotically with nearly every other lifeform in one way or another. I cannot overstate the importance of these unassuming decomposers.

I’ve added only a small sample of these cool creatures to the timeline, but I hope they inspire a lot of follow-up work for your students.  

Extinction Events

The original Montessori Timeline of Life has only four mass extinctions depicted. They are all shown as ice ages, and they are in the wrong places. The Rhyme and Reason Timeline of Life has them placed and represented more accurately.

• The first mass extinction event was at the end of the Ordovician Period. It was an ice age caused by plants.
• The second extinction event occurred at the end of the Devonian Period, another ice age caused by plants.
• The third mass extinction at the end of the Permian Period was caused by CO₂ and oxygen “rebalancing.” Major volcanic activity, fungi and plants all played a part.
• The fourth mass extinction at the end of the Triassic Period was triggered by major volcanic activity.
• The fifth mass extinction was of course the one that killed the dinosaurs at the end of the Cretaceous Period. 75% of living species were eliminated by heat! Read an awesome paper about it here.

Resources

• From Rhyme and Reason Academy
  • Product: The Timeline of Life
  • Product: Mute Timeline of Life
  • Product: Clock of Eons
  • Product: Geologic Time Cards
  • Blog Post: The Second Great Lesson | Complete Lesson Script and Resources
• Priscilla Spears Materials
  • Outline of Geologic Time and History of Life – Indispensable guide for anyone teaching the Montessori Timeline of Life
  • The Story of Mammals – Great follow up lesson for upper elementary students
  • What Goes on the Timeline of Life? – Blog post that I wish I would have found before I finished my timeline. It contains great information about why the original timeline needed to be updated.
  • Make Your Own Timeline of Life – Another blog post I wish I had found before finishing the timeline.
• Books on Amazon (affiliate links)
  • The Story of Evolution by Katie Scott – Up to date information and has a lot of matching creatures from my timeline.
  • Mushrooms Demystified by David Arora – This is the best mycology field guide, hands down.
  • Dinosaur Encyclopedia by Dr. Thomas Holtz – Well written and very accessible.
  • Life Story by Virginia Lee Burton – A classic book to have in the classroom.
• Optional props on Amazon (affiliate links)
  • Cambrian sea creature models
  • Fossil collection

Remaking the Montessori Timeline of Life was a labor of love. It’s something I’m excited to share with my students, and I hope you’re excited too. What are your thoughts? Have I gone too far? Should the material be left as is? I’d love to hear in the comments below.