“If I had more time, I would have written a shorter letter.” –Mark Twain*
Prior to our arrival at Corozal lab at the ACP facility, the PCP-PIRE Boots on the Ground interns prepared washing stations with tarps, buckets, hoses, and screens for sorting different particle sizes labeled by collection site. Our goal for the morning was to sort and clean our shells for travel through US customs and use in our classrooms.
As we scrubbed away sediment and loose dirt, teachers handled and examined each specimen. Some shells crumbled while others revealed insights into invertebrate ecology and the chemistry of fossilization. Professor Jon Hendricks and my colleague, Karen Schmidt explained why a few of my fossils had yellow crystals (calcite) in the shape of the shell whorls. Prior to cleaning my shells, I didn’t realize that as moisture with calcium carbonate precipitate evaporated out of the shell whorls, it crystallized and hardened. Later in the geologic process, bits of shell eroded away to reveal the rock-hard yellow crystals which held the interior shape of the original shell. Similarly, I was suddenly able to see the inner structure of the Arcitechtonica shells, which made the anatomy of the animal more clear to me. This was more of a thin long, body fitting into a narrow aperture. This was not the thick, muscular mollusc that I’d pictured while collecting shells caked with mud at Gatún.
As teachers worked, we asked ourselves and the scientists among us how we might teach our students to differentiate between small individuals from a species with a wide range of sizes from similar-looking species with a narrow range of small sizes. We chatted about how shell fragility might relate to ecology and relative abundance in the fossil record. We discussed project-based learning for students in grade 3 all the way through AP Biology and how students might use our fossils to construct new knowledge about invertebrate anatomy, ecology, fossilization, geology, and chemistry. As a middle school teacher, it was particularly informative to have a casual vertical collaboration around one specific type of artifact. I found myself reflecting on the teaching strategies that my students have relied on in elementary school, and I was able to get a glimpse of the lesson planning processes and rationales that their future high school Biology teachers might use. This helps me calibrate my own expectations and it reminds me to relate to my students as learners on the K-University path (and beyond), rather than simply as 8th graders.
After we screen washed our fossils, we made the final calls: Which samples were durable enough for classroom use and international flights? What would be most useful for the lessons we’d planned at the Biomuseo? What could we share between local colleagues once back in the states? What would be redundant to the collections we’ve been borrowing from past GABI RET participants in our district?
Meanwhile, Professor Jon Hendricks washed and prioritized what he would bring back for his cone snail work in San Jose. He hawked his shell rejects to the teachers: “I have a fine specimen here! A complete kauri margin up for grabs!” I put my hand out and received what looked to be a common broken shell with a ribbed texture and thought about my students. This fragment could seem mundane at a glance, but I hoped that my science illustration lesson would help make it a bit more exciting as students used broken kauri shells to visualize and create accurate, complete kauri drawings or models. “Get it while it’s hot folks! I have here a shell of an adorable googly-eyed gastropod!” Hands shot up and I realized that even superficial enthusiasm for the animals that once lived in these shells instantly made them more relatable and intriguing. I considered how an animal might look coming out of the shells and realized that this is one component of a lesson I’ve been working on: students gathering evidence and making educated guesses about the morphology of the shells’ inhabitants. Again and again on this trip I am seeing science as both a teacher and a student at the same time. It’s rare but incredibly useful to overlap these perspectives so I can improve my delivery of content and structure of activities to simulate and interact with university-level science.
PCP-Pire Assistant Supervisor Jorge Moreno, Professor Bruce McFadden, Dr Nathan Jud, and the interns collected and packaged cataloged research specimens from the ACP lab to get them to Florida with proper permits from the Panamanian government. Like the teachers, the this group prioritized samples and specimens which would be important for research and databases referenced by UF, PCP-PIRE, museums, and the Smithsonian. Research materials were wrapped, double-checked for permits, weighed, and packed. As the suitcases full of fossils were too heavy, the group reevaluated what could stay at ACP until next time. Again, the teacher process mimicked the scientist process and we teachers learned by professional examples of doing real, useful work; just as we plan to lead our students to learn by doing—even when that means including some of the less glorious processing that surrounds the actual scientific discovery.
We drove back to STRI, walked to the café for espressos and empanadas, and then went up the hill to CTPA for 2 talks. Our first talk, “The Holocene in tropical Mexico: Critical transitions of a non-stationary system,” examined the highly variable Quaternary climate cycles. Presenter Alexander Correa-Metrio and other researchers from the Universidad Nacional Autónoma de México have documented large variations in the climate biotic records in the Yucatán Peninsula and the rest of Central America within both longer glacial and shorter interglacial periods. They looked at interactions between climate, vegetation, and human occupation at diverse temporal and spatial scales and explored which factors have been associated with high frequency environmental variability.
Finding sediment sequences to represent the entire spectrum of the last 10,000 years has been an issue with their study. Still, there were relatively stable sedimentation rates, which has been an asset for identifying many pollen morphotypes. In the pollen analysis, Poaceae (grasses) were compared to Quercus (oaks) and Moraceae (other woody trees). Yucatán forests between 10,000-6,500 years ago were dominated by Moracea, and then Poaceae began to clearly dominate the pollen spectrum. Around that time, Zea mays also begins to show in the pollen record. The geo- and bio-indication records mostly show a loose correlation, with the exception of a “reorganization” period between 6,000-10,000 years ago. Biogeographic indications did appear to illustrate a “tipping point” for the climate system found in tropical Mexico through high variance, flickering, increased skewness, and jumping to a different state in the system. To close the talk, Correa-Metrio thanked the Lacandon Community and other academic supports.
Dr. Amanda Waite, one of the scientists from our GABI RET group, then gave the second CTPA talk titled: “From Ocean Gateway Closure to Land Bridge Exposure: Insights from Caribean Paleoceanography”. The talk began with an overview of the uplift of the land bridge and closure of the Central American Seaway and the GABI. Dr. Waite revisited the on-going debate surrounding the timing of closure and spoke about the strengthening of gulf stream, North Atlantic deep water circulation, glaciation, and other climactic changes as a result of changes in ocean temperatures, salinity, and depth, as well as evaporation rates and locations. She compared biotic indicators with abiotic marine records concerning the timing of the close of the isthmus. Dr. Waite is also bringing home matrix from Chagres, Bayano, Alajuela, and the Gatun formation to expand the paleontological and paleobathymetric records. With her data, Dr. Waite is working to improve models of ocean currents and depths relative to climate.
After explaining her research methods with Nd ratios in microscopic fish teeth found in deep sea cores, Dr Waite reiterated the point that “final closure of the isthmus” does not mean the same thing for each of the records different scientists from different disciplines are examining. This helps explain (and maybe resolve) some of the debate in timing of the rise of the isthmus, again reminding us that the GABI and the associated phenomena during the Neogene period are more accurately described as processes, rather than events. As a teacher and as a learner, the dynamism and complexity of processes that took place over millennia was an important reminder we heard multiple times from different scientists in the field and at CTPA and Tupper talks.
As the talks wrapped up, we left CTPA, literally driving off into the sunset. With a week and a half of intense hands-on field work spanning the whole width of Panama, graduate level talks spanning a range of scientific disciplines, journal articles and pool side reflections, lesson planning, and cultural immersion behind us, and with only one more day of field work to come, our group was both exhausted and excited upon arrival in Colón. We finished the day with a late-evening pool-side debrief of Professor Hendricks’ article on cone shells, the CTPA talks we’d heard earlier, and the plans and goals for Thursday’s Chagres beach fieldwork.
*Or Blaise Pascal, depending who you ask.