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(Theodosius Dobzhansky, 1973)

• “Nothing in biology makes sense except in the light of evolution.”

Understanding Biology…
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What is biological evolution?
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Human Evolution and the
Nature of Science

Evolution & NOS
• As the common thread in biology, the topic of evolution can help students make sense of diverse biological concepts. 4

Common Misconception about
Human Evolution
– Man evolved from apes or chimps… chimps… – No, Chimpanzees and humans had a common and less specialized ancestor
– Common Chimp = Pan troglodytes
– Human = Homo sapiens
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In the Origin of Species, Charles Darwin makes reference to human evolution only once when he writes “light will be thrown on the origin of man and his history.”

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It is of no surprise that much light or evidence has been gathered by paleoanthropologists – which include scientists who study human evolution – since
Darwin’s book was first published in 1859.

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In the last two years alone, both in science/research journals and in the public media, there have been numerous scientific articles, news reports, radio broadcasts, etc. describing further evidence of human or hominin (which include present day humans and their ancestors) evolution.
The evidence collected ranges from new fossils being unearthed to new hominin species being described such as the discovery of the “Hobbit” scientific name:
Homo floresiensis on the Indonesian island of Flores
(Morwood, Sutikna, Roberts 2005).
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The Nature of Science
• The discussion of human evolution provides biology teachers with something else – a significant opportunity to exemplify important lessons involving the
Nature of Science (NOS).

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The Nature of Science
• Biology teachers have an opportunity to address both past and current human evolution content, along with asking students nature of science questions such as
“How do we know?” and “What does the evidence reveal?” • These types of questions can help students examine evidences of our past while at the same time providing an opportunity to define nature of science terms such as
Hypothesis, Theory, and Law. Biology teachers can use recent discoveries in human evolution to demonstrate that science is a self-correcting process and that science demands and relies on empirical evidence.
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Scientific Law vs. Theory
• What is a Law?

• What is a Theory?

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Laws and Theories
• In the language of science, laws and theories are related but distinct kinds of scientific knowledge.

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Biological Evolution Defined
• Biological Evolution is defined as the change in allele frequencies
(where alleles are versions of the same gene that differ in their base sequence) within populations
(Freeman and Herron, 2004).

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Biological Evolution Defined
• Biological Evolution the changes in the genetic composition of a population with the passage of each generation (Volpe & Rosenbaum,
2000).

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Natural Selection Defined
• Natural Selection is defined as the process in nature that causes evolution through differential reproductive success among members of a population; that success depends on genetically based and heritable variation in characteristics that confer relative advantage or disadvantage to the bearer
(Price, 1996).
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Natural Selection Defined
• Natural Selection is defined as those individuals in a population that
(genetically) are better able to survive and reproduce in a particular environment leave more offspring, which in turn carry a higher frequency of genes promoting adaptation to that environment
(Scott, 2005).
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Scientific Law vs. Theory
• Laws consist primarily as statements or generalizations made about natural phenomena. • Theories, however, consist of the explanation / mechanism for how the law works (McComas, 2003). Scientific theories are explanations that are based on lines of evidence, enable valid predictions, and have been scientifically tested in many ways. 19

Laws and Theories
• The Law of Biological Evolution

• The Theory of Natural Selection

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Scientific Law vs. Theory
• Sonleitner, (1989) makes the point that theory and law, are qualitatively different in what they are and what they do. He states that laws are generalizations about phenomena while theories are explanations of phenomena.
• Theory and law are not distinguished by their degree of verification.
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Hypothesis?
• A hypothesis on the other hand provides scientists with an informed or educated explanation based on current empirical evidence. A hypothesis is much more than a mere prediction or forecast of an event and makes it much more amenable to testing and falsification. A hypothesis needs to be further tested in a repeatable fashion and which multiple lines of empirical evidence need to be collected from which an accepted scientific explanation or theory can be generated.
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Recent scientific findings
• Just in the past two years, two newly discovered hominin fossils have added on to the current day evidence of one hominin species, Australopithecus afarensis, and have forced biologists to reconfigure the human family tree by adding on another hominin species namely Homo floresienses. 23

Recent scientific findings
• Scientists have recently unearthed the 3.3 million year old fossilized remains of a little girl of three.
• Discovered in the Ethiopian Rift Valley where another famous Australopithecine named Lucy, a 3.2 millionyear-old adult, was discovered in 1974 along with a host of other hominin fossils ever since. T
• The finding of this fossil is the most ancient infant and complete fossil skeleton of A. afarensis. As a result, scientists suggest that this find not only provides key evidence in the evolution of hominins it also provides scientists with a window on how this species lived, grew and developed (Sloan 2006).
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Recent scientific findings
• Another recent hominin find which has made headlines in both scientific circles and across major newspapers around the world and for which numerous documentaries have been aired, has been referred to as Homo floresiensis or simply as “the Hobbit” as in J.R.R. Tolkien’s imaginary character. (Morwood, Sutikna,
Roberts 2005).
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Homo floresiensis
• Skeleton of adult human-like species
– Female
– Three feet tall
– Radiocarbon dated to only 18,000 years ago (a time when Homo sapiens also existed
• Discovered on Flores Island, in Indonesia
• New species is believed to be descended from Homo erectus, the closest known relative of Homo sapiens
(modern humans).
• Small size may be attributable to “island dwarfing.”
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Flores Island

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How Questions?
• Providing students with current information on the aforementioned hominin fossil discoveries, biology teachers can engage students to ask scientifically oriented questions such as “how did the bones of these ancestors become fossilized?” and
“how did H. floresienses arrive on the island of Flores 18,000 years ago and evolve physical characteristics that stopped growth at one meter for adults?”
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NOS Connection
• In doing so, students can begin to examine two critical aspects of the nature of science: (1) developing an understanding of hypotheses, theories and laws in science and (2) collecting evidence and providing explanations based on the evidence. 29

Biology Content & the NOS
Connection
• By presenting students with recent fossil discoveries, teachers have a unique opportunity to instruct their students on not only the science of nature, but also the nature of science. science 30

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Human evolution and empirical evidence • Science relies solely on empirical evidence, including human observations of natural processes.

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Human evolution and empirical evidence • Inferences and explanations about natural phenomena are tentative and can change when new evidence or data becomes available.
• The majority of scientists around the world agree that evolution occurs among organisms and that the mechanism for evolution, namely natural selection, is responsible for causing speciation
(i.e., one species evolving into another). All organisms on Earth, from bacteria to Homo sapiens (humans), have undergone speciation, with natural selection being the primary cause.
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Phylogenetic tree of primates

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Human evolution and empirical evidence • By examining the recent findings on the island of
Flores and by researching the fossilized evidence of Homo floresiensis, students can refer to questions about island biogeography and the environmental pressures which exist on islands (i.e. limited space and food supply) which can lead to some species shrinking over time. • One hypothesis currently being debated in the scientific community is whether or not the tiny
Homo floresiensis may have evolved from a population of Homo erectus that reached Flores some 800,000 years ago.
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Same Genus?
• Genetic tests comparing DNA from humans, chimps, gorillas and orangutans reveal striking similarities in the way chimps and humans evolve that set them apart from the others (Guardian, Jan. 24,
2006).
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Same Genus?
• The finding adds weight to a controversial proposal to scrap the long-used chimp genus
Pan and reclassify the animals as members of the human family. The move would give chimps a new place in the pecking order alongside humans, the only survivor of the genus Homo.
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Same Genus?
• According to scientists, the findings suggests some human traits only emerged 1 million years ago, a fleeting moment on evolutionary scales
(Proceedings of the
National Academy of Sciences, 2006).
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Same Genus?
• This study provides further support for the hypothesis that humans and chimpanzees should be in one genus, rather than in two different genera, because we not only share extremely similar genomes, we share similar generation time (Yi, 2006).

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Implications for teachers and instructional strategies
• A variety of instructional strategies are available for teachers to use in the classroom that target a multitude of learning styles among students. These strategies include but are not limited to reading assignments, classroom activities and scientific debate.

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Reading assignments
• A book chapter available on-line http://www.bscs.org/library/Evolutionary_Science _complete.pdf
• The Human Species on the Tree of Life (Kimbel
2005), outlines the scientific evidence for human evolution. • The article also contains numerous examples of the various lines of evidence – both direct and indirect (i.e. comparative morphology, biogeography and human origins, comparative anatomy of DNA, and the fossil record) – which scientists are currently using to better understand past human evolutionary events. 40

Reading Assignments: Books
• Books that are useful include:
• The Third Chimpanzee: The Evolution and
Future of the Human Animal (Diamond
1993) and
• The First Human: The Race to Discover
Our Earliest Ancestors (Gibbons 2006).

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Classroom activities
• To help students learn, in a more concrete way, how comparative DNA analysis is used by scientists, an activity that simulates genomics can be used (Flammer 2006).
• In this simulation, banding patterns are compared on the chromosomes of humans and apes. Degrees of similarities, and some causes of their differences are explored. Inferences about common origins based on those similarities (i.e. forensic markers) are also examined incorporating various science processes. “On the Web” features more teacher resources for classroom activities exploring human evolution and the NOS.
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Scientific debate
• Teachers can also plan scientific debates in class. Power point presentations and/or position statements on human evolution can be designed in which students provide various lines of scientific evidence to defend or refute current theories and/or hypothesis on human evolution and natural selection.
• In doing so, teachers provide an opportunity for students to engage in higher order thinking questions (Bloom’s Taxonomy/5 Es) and also take part in group discussions while targeting various features of the NOS.
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On the Web
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The Talk Origins Archive: http://www.talkorigins.org/faqs/homs/
This web site provides an overview of the study of human evolution and of the currently accepted fossil evidence. It contains analysis of individual fossils with a variety of digital images.

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University of California Museum of Paleontology at UC
Berkeley and the National Center for Science Education: evolution.berkeley.edu/evolibrary/home.php This is a good website for labs that explore human evolution and the
NOS.

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Evolution and the Nature of Science Institutes: http://www.indiana.edu/~ensiweb/home.html This website contains multi-media and in-depth lesson plans and activities, developed by leading science educators.
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References
DeSilva, J. (2006). Interpreting Evidence: An approach to teaching human evolution in the classroom. Retrieved August 17, 2006 from http://www.mos.org/evolution/downloads/desilva.html Diamond, J. 1993. The Third Chimpanzee: The Evolution and future of the Human
Animal. New York: Harper Perennial Publishers.
Flammer, L. 2006. http://www.indiana.edu/~ensiweb/lessons/chr.con2.html.
Gibbons, A. 2006. The First Human: The Race to Discover Our Earliest Ancestors. New
York: Doubleday.
Kimbel, W.H. 2005. The human species on the tree of life. In J.C. Cracraft and R.W.
Bybee (Eds.), Evolutionary science and society: Educating a new generation pp. 5268.Colorado Springs, CO: BSCS.
Morwood, M., T. Sutikna and R. Roberts. 2005. The people time forgot. National
Geographic, 207 (4) pp. 2-12.
Sloan, C.P. 2006. Origin of childhood. National Geographic, 210 (5) pp. 148-159.
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