What goes on a timeline of life? November 05 2020, 5 Comments

Suggestions for evaluating a timeline of life.

A suggestion for studies of the timeline of life October 20 2017, 0 Comments

The timeline of life is a vital part of cosmic education. It gives children a vision of how life has changed through time and an important perspective for appreciation of today’s life on Earth.

I have been frustrated with the many errors and misconceptions that are portrayed on the traditional Montessori timeline of life. Another material, not from the Montessori world, has come to my attention. It is from What on Earth? Books, . Author Christopher Lloyd and illustrator Andy Forshaw have done several “Big History” type timelines. These publications can give children a valuable framework of how life has developed and changed through time.

In order to show a variety of life and tie it into human civilization, the timeline uses different timescales across its length. This could lead children to a false picture of the time elapsed between the events depicted. You can help them understand the true duration of the various geologic time periods if you display the time periods to scale above the timeline in the What on Earth? Wallbook of Natural History: From the Dawn of Life to the Present Day

I did this for the 2.3 meter-long edition, published 2013. This book is 16.5 inches or 42 cm tall. I made a timeline that shows the true proportions of the geologic time periods. The second strip of paper beneath it shows the time periods as shown on the timeline. Here are the views from the formation of the Earth end and the present end. You can see that the Hadean Eon (black), Archean Eon (yellow), and Proterozoic Eon (pink) portions have vastly different shares on the two scales.

For example, the Hadean Eon is 31 cm long on the actual timescale, and 3.4 cm long on the timeline. The Cenozoic Era is 3.4 cm long on the actual scale, and the Holocene Epoch would be microscopic. On the What on Earth timeline, the Cenozoic Era is 46 cm, with 23.5 cm of that being devoted to the Holocene and Anthropocene. (If you would like the measurements for my two timelines, please email me.)

This timeline gives most of its length to the Phanerozoic Eon (Paleozoic, Mesozoic, and Cenozoic Eras), which is appropriate. The traditional Montessori timeline of life shows the events of the Phanerozoic Eon, even if it does not carry that label. When one looks at the What on Earth timeline from the end that shows the present, the Cenozoic Era has internal scale changes for emphasis on human events.

Nevertheless, I think the What on Earth timeline would be a good introduction to the changes in life through time. Having the life in the oceans shown separately from life on land helps children keep track of the two different environments. There are a few things you will need to correct/explain. The synapsid lineage is shown, but it is called “mammal-like reptiles,” an older term that paleontologists have dropped. Likewise, I would change the term “dicots” to “eudicots,” the term botanists use. Eudicots (true dicots) are the old dicots minus the magnoliids. At least the eudicots are there on the timeline, along with a good array of accurately portrayed prehistoric plants, a part that is often missing from timelines of life.

The What on Earth book or timeline is available in several sizes. There is a newer edition that is smaller and 6 feet long. You may need the magnifier, a flat, plastic Fresnel-type, that comes with the book, to read all the fine print. The timeline is available in a larger, 10-ft. edition as well. It is available on Amazon or on the What on Earth website. . It costs $40-50, and the smaller version costs $15-$20. At present, the nature (history of life) timeline is available in Japanese, Chinese, Korean, Taiwanese, American and Dutch. German, French, and Italian are in the works. The What on Earth Big History timeline is available in 15 languages, but the history of life takes up only about a third of it with human history displayed on the rest. See the What on Earth website of further information.

You may choose to make your own timeline. If so, my publication, Outline of Geologic Time and the History of Life, can help you. See .

Happy explorations of life through time.

The Tree of Life versus the Timeline of Life March 29 2017, 0 Comments

Someone has posted my Tree of Life chart on Pinterest and suggested in the caption that it could be a substitute for the Timeline of Life. NOT SO! These are two different materials with two different uses.

The Tree of Life does not show details of life through time. It shows extant animals and their lineages. People may be confused because classification has an element of time now. We group organisms by their common ancestors. You can’t show relatives without some reference to time. My cousins and I share a set of grandparents, so we have a recent common ancestor. That’s what makes us closely related.

Classification has become systematics (more on that in a later post). Biologists do not show rows of evenly spaced boxes with no connections when they diagram a kingdom or other related life. Instead, they connect the boxes (or names) with a branching diagram to show which organisms share more recent common ancestors.

The Tree of Life chart is used much like a Five Kingdoms chart was. If you are still using a Five Kingdoms, Six Kingdoms, or heaven forbid, a Two Kingdoms chart, you need to change to a different kind of chart. A Tree of Life chart is used to introduce children to the diversity of life. When I give this lesson, I tell children that this chart has a branch for all the major kinds of life on Earth. (And you may have one precocious child who asks “What about viruses?” No, they don’t belong on the organisms’ Tree of Life. They have their own.)

I can envision directing children’s attention to the big, black branches and noting that they are all connected, and they all share a common origin. I would also say that there are many, many varieties of life, and we would have a hard time studying it all at once. Instead, we put certain branches together for the purpose of focusing on them. Three of these major branches are called kingdoms because they are all the descendants of a common ancestor. They are outlined with color rectangles – yellow for fungi, red for animals, and green for land plants. The other two rectangles show organisms that we put together for the purposes of study – purple for prokaryotes and blue for protists.

The Tree of Life is used for children ages 6-9 to show them the big overview of life. They enjoy putting the cards on the solid, colored rectangles. The text on the back of the illustrations helps children place the picture of the organism. To help them find the right place, the major section and the name of the branch are in bold typeface. Older children and even secondary level students can still use the Tree of Life, and they should have an opportunity to place the cards and discuss this chart. Do they see that animals and fungi are sister kingdoms? This is why treating fungal infections is so hard.

On the other hand, the Timeline of Life shows the organisms that have lived during the time periods of the Phanerozoic Eon. A few timelines may have a bit of the previous Late Proterozoic, but the major emphasis is on life since the beginning of the Cambrian Period. There is nothing other than a timeline of life that can show this. Unfortunately the traditional Montessori Timeline of Life is riddled with mistakes – omission of the five major extinctions, all extinctions shown as ice ages, indistinct organisms, no grouping of related organisms, and my worst pet peeve, converging red lines that seem to show several lineages being fused into one.

OK, enough attacks on the Timeline of Life. It is still an important material for children, and I think it is important to use one that is updated and corrected, either by the teacher or by a company that has carefully researched its product. The Timeline of Life helps children understand how life has changed through time. (One last rant – add the Devonian explosion of plants! During that period, the land turned green as plants changed from a low green fuzz to trees that bore seeds. The Devonian – It’s not just for fishes!)

As a reminder of what is available on my website to aid you, my Outline of Geologic Time and the History of Life has lots of information that will help you make an accurate, up-to-date Timeline of Life. The Tree of Life chart is still a free download – my gift to the Montessori community. My book, Kingdoms of Life Connected, is a teacher’s guide to the tree of life. I updated it in the fall of 2016.

May you and your children enjoy exploring the living world, both its diversity and its history.