Month: December 2016

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Children’s Books About Evolution

Evolution is a difficult subject to learn, let alone teach. Because evolution is generally such a slow process, it involves a timeline that is challenging for us to comprehend. Evolution is also commonly misunderstood, so misconceptions abound, be they purposeful misrepresentations, gaps in understanding, or otherwise. Wrapping one’s brain around even the basic tenets of evolution can take years of study, yet it is one of the most fundamental concepts of biology; failing to understand it stifles one’s knowledge of and appreciation for the study of life on Earth. On the flipside, gaining an understanding of the workings of evolution can inspire a greater appreciation for our place in the universe and can instill in oneself the urgency of conservation.

Despite being a tough subject to grasp, there is no reason why children should be exempt from learning about it. However, because it is such a complex topic, adults can struggle to find ways to explain it. Luckily, there are some great children’s books about evolution that introduce the subject in basic ways. These books are good starting points and can help cultivate a desire to explore the topic further. Understanding evolution and the science surrounding our world and the broader universe is a lifelong pursuit. Children will benefit from a head start.

What follows are reviews of a handful of books that may be useful in teaching kids about the theory of evolution.

I Used to Be a Fish by Tom Sullivan

i-used-to-be-a-fish

This book is an excellent place to start. It is a quick and easy read, and it introduces – in a very simple way – the evolutionary lineage of humans. It doubles as a lesson on evolution and, as Sullivan puts it, “a tribute to every child’s power to transform their lives and to dream big,” which is achieved by highlighting the imagination of the main character and defining evolution as the gradual development over a lifetime towards achieving goals and aspirations.

In the Author’s Note, Sullivan briefly explains some important aspects of evolution: it is “a very slow process” that “occurs over generations to entire populations of creatures,” it doesn’t occur in a straight line like the book implies but instead looks “more like a tree with many complicated branches,” and “it doesn’t happen because a creature wants it to.”

One step in our evolutionary lineage as depicted in I Used to Be a Fish by Tom Sullivan

One step in our evolutionary lineage as depicted in I Used to Be a Fish by Tom Sullivan

Life history

Timeline from I Used to Be a Fish by Tom Sullivan. Look how far we’ve come!

Grandmother Fish by Jonathan Tweet; illustrated by Karen Lewis

grandmother-fish

This book is similar to Sullivan’s book, but it adds a little more detail to the story and invites interaction from its audience. As major periods in our evolutionary lineage are reached, readers are asked to “wiggle” like our Grandmother Fish, “crawl” like our Grandmother Reptile, “squeak” like our Grandmother Mammal, “hoot” like our Grandmother Ape, and so on. As the story transitions from one main character to another, simplified versions of evolutionary trees are shown (like the one below).

grandmother-fish-2

A larger version of “Our Evolutionary Family Tree” is featured at the end of the story followed by several pages of additional information that adults can use to further explain evolution to children, including discussions on three major concepts of evolution (descent with modification, artificial selection, and natural selection), more details on the main characters in the book, and a guide to correcting common errors about evolution.

grandmother-fish-3

When Fish Got Feet, Sharks Got Teeth, and Bugs Began to Swarm by Hannah Bonner

when-fish-got-feet

This book is much more text heavy than the first two, but is still very approachable. The illustrations are both humorous and informative, and Bonner excels at explaining complex topics in a way that makes them easy to digest. Rather than covering hundreds of millions of years of evolution like the first two books, this book focuses mainly on events that occurred during the Silurian and Devonian periods – between 360 and 444 million years ago. It was during this time that plants were making their way to land and diverging into many different forms. Arthropods were doing the same. During this period, the earth’s atmosphere became more oxygen rich and soil began to accumulate largely due to the growth and expansion of land plants.

Recipe for a land plant from When Fish Got Feet by Hannah Bonner

Recipe for a land plant from When Fish Got Feet by Hannah Bonner

This was also a period of great diversification in the fish world. Jaws were becoming more common and skeletons made of bone (as opposed to cartilage) were developing.  The first tetrapods (fish with legs) emerged from the oceans and onto land in the Devonian period. These tetrapods were our early ancestors, and Bonner explains how some of the skeletal features that fish developed during this time period were precursors to our current skeleton.

Unlike the first two books, the evolution of plants receives some attention in Bonner’s book. It is during the Devonian period that the first trees and seed-bearing plants appear. As in the other books, there are additional resources at the end, including this important warning by Bonner: “Please remember that anyone can set up a Web site, so not everything you will encounter will be good science.”

A time line of life on earth from When Fish Got Feet by Hannah Bonner

A timeline of life on earth from When Fish Got Feet by Hannah Bonner

Key to helping children understand evolution is understanding it ourselves, and there are, of course, endless resources out there to help with this. I will suggest just two additional books. In keeping with the spirit of children’s books, there is a great illustrated biography of Charles Darwin (who is considered the Father of Evolution) called Darwin For Beginners by Jonathan Miller and Borin Van Loon. It’s basically Darwin’s life told in graphic novel form. And keeping with the fish theme, you can’t go wrong with Neil Shubin’s, Your Inner Fish, a fascinating look into the origins of many of the parts, pieces, and other features of the human body.

Do you have a favorite book, children’s or otherwise, about evolution? Please share it in the comment section below.

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Ethnobotany: The Henna Tree

A hair dye used in pre-dynastic Egypt is still used today. This enduring plant-based dye has found its way into a great number of cultures going back as long as 6000 years. Its popularity is thanks in part to the broad distribution of the plant itself, but is largely a result of the diverse religious traditions that have incorporated the dye into their rituals. The plant’s use in such traditions continues, while its current popularity extends well beyond that.

Lawsonia inermis is the only species in its genus. It is a member of the plant family, Lythraceae, a family that includes crepe myrtles (Lagerstroemia), cigar plants (Cuphea), and pomegranates (Punica). L. inermis has many common names, including mignonette tree and Egyptian privet. It is most commonly known as, henna, a term that refers to the plant itself, the dye derived from the plant, and the body art made using the dye.

Henna is a shrub or small tree that reaches a height of about 6 meters. The leaves are smooth, elliptically-shaped, and oppositely-arranged on branches that are spine-tipped. Inflorescences are many-branched with numerous small, fragrant flowers. The most prominent features of the flowers are four sepals forming a bowl shape and several white to red stamens reaching towards the sky. The fruits are small, round, brown capsules full of tiny seeds. Henna thrives in dry environments with poor soil; however, it does not tolerate frost. It occurs in tropical and subtropical regions of Africa, western and southern Asia, and northern Australasia. Cultivation by humans has broadened its distribution well beyond its original boundaries.

Lawsonia inermis - photo credit: wikimedia commons

Lawsonia inermis – photo credit: wikimedia commons

Henna has been used to dye the skin, nails, and hair of women and men in many cultures and religions across its area of natural distribution and beyond. Its use has been especially common among women as part of fertility and marriage celebrations. The plant’s dye may have been first discovered around the mouths of browsing livestock – the persistent red-orange color having the appearance of blood. Henna plants are drought-deciduous, but they burst back to life when rain returns, producing abundant new branches, leaves, and flowers. This period of growth coincides with celebrations of marriage and fertility and may explain why it found common use in such traditions.

Dyes are made by crushing dried leaves into a fine powder and then mixing it into a paste using water, lemon juice, tea, or other liquids. A soap or shampoo is produced when henna is mixed with plant extracts containing saponin, and the addition of certain essential oils can enhance the performance of the dye. The compound in the leaves that produces the red-orange dye is called lawsone and is found in varying concentrations depending on the conditions in which the plant was grown. High heat and low soil moisture is said to produce the highest levels of lawsone. More than just a dye, lawsone also has antifungal properties and strongly absorbs UV light, thus its application is beyond cosmetic as it has proven useful against fungal diseases like athlete’s foot and as a sunscreen. And that’s just the beginning.

Henna applied to hair - photo credit: wikimedia commons

Henna applied to hair – photo credit: wikimedia commons

A study published in the Journal of Ethnopharmacology by Semwal, et al. reveals that nearly a hundred phytoconstituents (or “biologically active compounds”) have been isolated from all parts of the henna plant. Henna has long been used medicinally to treat a wide range of ailments, and while it may not be an effective treatment for all that it has been historically used for, it has been found effective for certain things and has great potential for further use.

In the paper, the authors review dozens of studies exploring the many “biological activities” that henna is claimed to have, which include “antifungal, antibacterial, virucidal, antiparasitic, anti-inflammatory, analgesic, and anticancer properties,” etc. Research into these properties is limited and has been “complicated and hampered” by the widespread practice of adding other ingredients (some of them harmful) to henna products. In order for henna’s “therapeutic potential” to be properly explored, the authors advise identifying and standardizing the plant’s active components.

Henna continues to be used in cultures across the world and is particularly prominent in Hinduism and Muslim practices. It is most commonly used to dye hair and create temporary body art (also known as mehndi). Henna art is often applied to the hands and feet, where the skin is thick and absorbs more of the lawsone. It is applied as a paste and either squeezed through a plastic cone or syringe or painted on with a stick or brush. The longer the paste is left on, the darker the stain will be. After a week or so the henna begins to fade as old skin cells slough off.

photo credit: wikimedia commons

photo credit: wikimedia commons

In ancient cultures, henna was thought to ward off the Evil Eye as well as bring good luck and blessings, a trait known as baraka. This belief is part of the reason why henna was incorporated into marriage ceremonies and other religious rituals. Because of henna’s antifungal, analgesic, and anti-inflammatory properties, etc., real benefits are seen when henna is applied to various parts of the body. Semwal, et al. argue that a scientific understanding was not necessary for “recognition of benefit.” Today however, “scientific investigation and quantification of henna’s ‘baraka’ should expand and optimize these traditional qualitative understandings.”

Because of henna’s widespread use and long history, it is not feasible to fit henna’s entire story into a single blog post. Henna is worth exploring on your own. Here are a few more interesting tidbits for now. In Semwal, et al.’s summary there is a mention of henna twigs being “rubbed over the teeth for effective dental self-care” – something to keep in mind in case you find yourself without a toothbrush, and a henna plant happens to be nearby. A paper published in a 1993 issue of Thaiszia – Journal of Botany discusses the historical use of henna in the Balkans. Slavs in the area reportedly treated typhoid fever using a mixture of henna and “the juice of twenty heads of garlic” heated in water. Finally, henna has been used to dye many things, including leather, cloth, and animal fur. Persians have long used henna to dye the manes, tales, and hooves of their horses and other animals. A practice that continues today.

More Ethnobotany Posts:

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What Is a Plant, and Why Should I Care? part four

What Is a Plant?

Part one and two of this series have hopefully answered that.

Why should you care?

Part three offered a pretty convincing answer: “if it wasn’t for [plants], there wouldn’t be much life on this planet to speak of.”

Plants are at the bottom of the food chain and are a principle component of most habitats. They play major roles in nutrient cycling, soil formation, the water cycle, air and water quality, and climate and weather patterns. The examples used in part three of this series to explain the diverse ways that plants provide habitat and food for other organisms apply to humans as well. However, humans have found numerous other uses for plants that are mostly unique to our species – some of which will be discussed here.

But first, some additional thoughts on photosynthesis. Plants photosynthesize thanks to the work accomplished by very early photoautotrophic bacteria that were confined to aquatic environments. These bacteria developed the metabolic processes and cellular components that were later co-opted (via symbiogensis) by early plants. Plants later colonized land, bringing with them the phenomena of photosynthesis and transforming life on earth as we know it. Single-celled organisms started this whole thing, and they continue to rule. That’s just something to keep in mind, since our focus tends to be on large, multi-cellular beings, overlooking all the tiny, less visible beings at work all around us making life possible.

Current representation of the tree of life. Microorganisms clearly dominate. (image credit: nature microbiology)

Current representation of the tree of life. Microorganisms clearly dominate. (image credit: nature microbiology)

Food is likely the first thing that comes to mind when considering what use plants are to humans. The domestication of plants and the development of agriculture are easily among the most important events in human history. Agricultural innovations continue today and are necessary in order to both feed a growing population and reduce our environmental impact. This is why efforts to discover and conserve crop wild relatives are so essential.

Plants don’t just feed us though. They house us, clothe us, medicate us, transport us, supply us, teach us, inspire us, and entertain us. Enumerating the untold ways that plants factor in to our daily lives is a monumental task. Rather than tackling that task here, I’ll suggest a few starting points: this Wikipedia page, this BGCI article, this Encylopedia of Life article, and this book by Anna Lewington. Learning about the countless uses humans have found for plants over millennia should inspire admiration for these green organisms. If that admiration leads to conservation, all the better. After all, if the plants go, so do we.

Humans have a long tradition of using plants as medicine. Despite all that we have discovered regarding the medicinal properties of plants, there remains much to be discovered. This one of the many reasons why plant conservation is so important. (photo credit: wikimedia commons)

Humans have a long tradition of using plants as medicine. Despite all that we have discovered regarding the medicinal properties of plants, there remains much to be discovered. This is one of the many reasons why plant conservation is imperative. (photo credit: wikimedia commons)

Gaining an appreciation for the things that plants do for us is increasingly important as our species becomes more urban. Our dense populations tend to push plants and other organisms out, yet we still rely on their “services” for survival. Many of the functions that plants serve out in the wild can be beneficial when incorporated into urban environments. Plants improve air quality, reduce noise pollution, mitigate urban heat islands, help manage storm water runoff, create habitat for urban wildlife, act as a windbreak, reduce soil erosion, and help save energy spent on cooling and heating. Taking advantage of these “ecosystem services” can help our cities become more liveable and sustainable. As the environmental, social, and economic benefits of “urban greening” are better understood, groups like San Francisco’s Friends of the Urban Forest are convening to help cities across the world go green.

The importance of plants as food, medicine, fuel, fiber, housing, habitat, and other resources is clear. Less obvious is the importance of plants in our psychological well being. Numerous studies have demonstrated that simply having plants nearby can offer benefits to one’s mental and physical health. Yet, urbanization and advancements in technology have resulted in humans spending more and more time indoors and living largely sedentary lives. Because of this shift, author Richard Louv and others warn about nature deficit disorder, a term not recognized as an actual condition by the medical community but meant to describe our disconnect with the natural world. A recent article in BBC News adds “nature knowledge deficit” to these warnings – collectively our knowledge about nature is slipping away because we don’t spend enough time in it.

The mounting evidence for the benefits of having nature nearby should be enough for us to want to protect it. However, recognizing that we are a part of that nature rather than apart from it should also be emphasized. The process that plants went through over hundreds of millions of years to move from water to land and then to become what they are today is parallel with the process that we went through. At no point in time did we become separate from this process. We are as natural as the plants. We may need them a bit more than they need us, but we are all part of a bigger picture. Perhaps coming to grips with this reality can help us develop greater compassion for ourselves as well as for the living world around us.

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Cedar Confusion

This is a guest post by Jeremiah Sandler. Words by Jeremiah. Photos by Daniel Murphy (except where noted).

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What makes a cedar a cedar?

I recently asked this question to a professor of mine because I kept hearing individuals in the field refer to many different species as “cedars”. It was puzzling to me because, being the taxonomy-nerd that I am, most of these plants are in entirely different plant families but still called the same thing. Yes, sometimes common names overlap with one another regionally; avoiding that mix up is the purpose of binomial nomenclature in the first place! So, what gives?! Why are 50+ different species all called cedars?

This professor is a forester, not a botanist. He told me the word “cedar” describes the wood. Turns out, after some research and conversation, that’s all there was to it. As defined by Google, a cedar is:

Any of a number of conifers that typically yield fragrant, durable timber, in particular.

Cedar wood is a natural repellent of moths, is resistant to termites, and is rot resistant. A good choice of outdoor lumber.

I was hoping to find either a phylogenetic or taxonomic answer to what makes a cedar a cedar. I didn’t. Taxonomic relationships between organisms are one of the most exciting parts of biology. Thankfully, some solace was found in the research:

There are true cedars and false cedars.

True cedars are in the family Pinaceae and in the genus Cedrus. Their leaves are short, evergreen needles in clusters. The female cones are upright and fat, between 3 – 4 inches long. Their wood possesses cedar quality, and they are native to the Mediterranean region and the Himalayas.

False cedars are in the family Cupressaceae, mostly in the following genera: Calocedrus, Chamaecyparis, Juniperus, and Thuja. Their leaves are scale-y, fan-like sprays. Female cones are very small, about half an inch long, and remain on the tree long after seed dispersal. The bark is often both reddish and stringy or peely. Their wood possesses cedar quality. It is easy to separate them from true cedars, but less obvious to tell them from one another. These false cedars are native to East Asia and northern North America.

I couldn’t do away with the umbrella term “cedar.” Every naturalist can agree that one of the most pleasurable things while outdoors looking at plants is identifying them. I have set a new objective to correctly identify and differentiate between all of the cedars and false cedars, rather than simply calling them cedars. I guess I’m just fussy like that.

Weeping Blue Atlas Cedar (Cedrus atlantica ‘Glauca Pendula’)
Western Redcedar (Thuja plicata)
Cedar of Lebanon (Cedrus libani ‘Pendula’)
Northern White-cedar (Thuja occidentalis)
Deodar Cedar (Cedrus deodara ‘Prostrate Beauty’
Eastern Redcedar (Juniperus virginiana)