Observations- Part 2
Are humans a species?
Complete by January 28
1. To see how paradigms and epistemologies influence scientific concepts, like that of the “species”
2. To understand the multiple uses of the term “species”
3. To practice close observation, the foundation of the empirical part of science
The scientific name for humans is Homo sapiens, which follows the format Genus species. In this case, we are referring to the “species” as a “taxon” (plural: taxa), a named group of organisms that can be described. “Species” is also a “category” – it’s a ranked category in the Linnaean hierarchical taxonomy used to organize the diversity of life. Each rank fits within the previous – e.g., all primates are mammals, and all mammals are chordates. The human species fits within this classification system:
As opposed to the “species”, the other ranks in this taxonomic system are not unified in time/space and do not evolve as a unit – e.g., mammals have no singular common location in space, no common location in time because there are extinct and extant members, and do not evolve as one unit.
“Species” is a “concept” – it has changed throughout history and is influenced by paradigms and culture. From Plato to Charles Darwin, the predominant idea of a species in the western world was one of fixed species that did not change. This concept shifted to one of species that change over time after Darwin presented his theory of evolution by natural selection with substantial data showing changes in the fossil record, variation in morphology and geography, etc. Darwin conceptualized this change as slow, while others like TH Huxley thought it changed suddenly with long periods of stasis in between. Some, like Earnst Haeckl, thought that the path of evolution was linear, leading to humans as the pinnacle of progress. As new data was observed (like characteristic patterns of phenotypes resulting from cross-breeding experiments) and new concepts and theories were developed (like “gemmules” transforming into the “gene”), it led to new species concepts. At this point, the dominant scientific view is that the species is a concrete, describable entity in nature (that we generally describe based on its characteristics) and that species change (although we often think about an archetype individual made of its characteristics as representing a species). Different definitions emphasize different aspects.
There are still multiple operational definitions that seek to be able to define and identify species but no one definition is completely satisfactory. Different definitions emphasize different aspects of a species. These concepts are not necessarily in conflict, but may serve different, complementary functions.
Potentially operationalizable species concepts include:
● Typological (Aristotle, Linnaeus, etc.): “A class of objects, members of which shared certain defining properties” (p. 268, Mayr 1996) – generally the properties are morphological and/or genetic
● Biological (Dobzhansky, Mayr): “Groups of interbreeding natural populations that are reproductively isolated from other such groups” (p. 264, Mayr 1996) – can result from geographic isolation or isolating mechanisms that prevent species from fusing
● Evolutionary (Emerson, Simpson): “A lineage (an ancestral-descendent sequence of populations) evolving separately from others and with its own unitary evolutionary role and tendencies” (p. 153, Simpson 1961)
● Ecological (van Valen): “A lineage…which occupies an adaptive zone (part of a resource space)…different from that of any other lineage in its range and which evolves separately from all lineages outside its range” (p. 233, van Valen 1976)
Assignment: Your goal is to evaluate some of the assumptions and paradigms underlying the species concept by testing the extent to which your observations and analysis of human characteristics support the species concept. Identification of species by their morphological or genetic characteristics is based on comparing similarities and differences. As such, it is crucial to define how similar is similar enough to be considered the same species. Rather than just picking a number, you will work to develop a rule or set of rules defining “similar enough” with a clear rationale based on your close observation of many “species”. You will then 1) apply the rule(s) to humans, 2) put your analysis back in the context of what a species is, and 3) evaluate how your results are influenced by the underlying assumptions, epistemologies, and paradigms you hold. Since this is the first lab, we’ve got a set of instructions for you to follow:
1. DATE, TITLE, QUESTION, PURPOSE: See lab notebook guidelines. Notebook: Write these down!
2. PROCEDURE: Define your rule(s)
a. Closely observe several groups of things considered a single species. To do this, we recommend that you search the internet for images of the following: 1) school of fish belonging to the same species (note the species), 2) Herd of a land animal such as caribou, bison, elk, or buffalo (note the species) 3) a population of Cepaea snails, 4) a chart showing breeds of cats, dogs, chickens or pigeons, 5) sequences of DNA from the same species handed out in class (examples 1-4), 6) a field of snapdragons and 7) a congregation of monarch butterflies. Notebook: Write it down and record your observations of the similarities, differences, and variability within each group (you may need to draw)!
b. Develop a potential rule or set of rules. Notebook: Write it down!
c. Test your potential rule(s) by trying to apply it to all of your groups of things. Notebook: Write it down!
d. If you aren’t satisfied with your rule(s), try modifying it & doing more observations. Notebook: Write these down!
e. If you are satisfied, briefly explain your criteria for satisfaction. Notebook: Write these down!
3. PROCEDURE and DATA: Observe humans and apply your rule(s)
a. Go outside and closely observe human morphology (not behavior!). Notebook: Write down what you did in the procedure (including sample size, location, etc.) and record your observations of the similarities, differences, and variability (you may need to draw and use words) as data!
b. Look at the human DNA sequences found here (sets 1 & 2 on the last two pages) . Notebook: Record your observations – you may want to put a copy of the sequences to show what you did)
c. Apply your rule(s). Notebook: Record analysis in an organized way
d. RESULTS: Summarize the data and whether all humans observed ended up classified into one group, including one relevant data table or figure. Notebook: Write these down!
4. DISCUSSION: Explain and interpret the results,specifically including:
a. Whether your rule resulted in humans being classified as one group and what that means in terms of humans as a species
b. Why you might have gotten the results you did, including identifying specific assumptions, epistemologies, and paradigms that may have influenced the results
c. How your results relate to the species concept, specifically referencing the Mayr 1996 paper!
d. Implications for how you think about what a species is
5. ADD AN ENTRY TO THE TABLE OF CONTENTS
Tips & tricks:
● Make sure you include all required sections & follow formatting guidelines in your lab notebook! (I recommend printing out p. 2 of the Lab Notebook Guidelines and pasting it in the back of your notebook so you always have a checklist). Lab notebooks will be collected several times throughout the semester.
● Be very cautious that your assumption of all humans belonging to the same species does not bear influence on carrying out the procedure you developed. The goal here is NOT to classify every person you see as belonging to the same species but, rather, to create a method by which to classify organisms, employ this method on people, and evaluate how effective it was.