Aims
This course aims to:
- enable you to synthesise ideas on the basis of evidence
- provide information that helps improve our understanding of science within the
context of society
- introduce you to the unity of life on earth and an understanding of the molecular biology underpinning ‘Evolution through Natural Selection: the growth of an idea’
Content
For Charles Darwin, comparative embryology was important evidence in support of the evolution of descendants from a common ancestor. The biologist Ernst Haeckel was the German advocate of Darwinism, visited Darwin at home in 1866 and in that year published a revolutionary synthesis of Darwin’s ideas, including his (Haeckel’s) developed theory of an earlier idea that ‘ontogeny (embryonic development) recapitulates phylogeny (evolutionary history)’ … his so-called biogenetic law that dominated evolutionary thinking in the late 19th century.
Walter Garstang at Leeds University highlighted the problems of the biogenetic law in 1921, by pointing out that an adult cannot evolve directly into another adult. According to Garstang, embryonic development represents the stages of ancestors to whatever point it was in ontogeny when divergence into new forms occurred. In effect ‘ontogeny does not recapitulate phylogeny – it drives it’. He realised that the larval stages of adult forms of many animal taxa were in effect precociously hatched embryos and potentially the nodes for major evolutionary innovation that as the result of selection of larval characteristics consequently affected the adult stages of subsequent generations.
Garstang’s ideas attracted few adherents until the advent in the 1970s of the molecular genetic revolution that has transformed Biology and evolutionary thinking in our lifetime. Today, investigating the interactions of gene products controlling development and how these interactions might have changed through time resulting in the evolution of new taxa is now possible using the machine and molecular toolkits of molecular genetics. These new insights increasingly validate Garstang’s thinking.
Our aim will be to add to our understanding of evolution through natural selection by exploring a definition of evolution as: a modification through time of ontogeny (development) as the result of changes in gene regulation (where/when/how much gene product). The programme Evolution through Natural Selection … will seek to help our understanding of this thinking through the examination of case studies set within the historical context of the evolutionary thoughts of earlier pre-Darwinian and post-Darwinian times … the growth of an idea indeed. The sessions will explore a synthesis of these ideas to reassess the nature of evolution in process.
Presentation of the course
The course will be presented through PowerPoints, each for one of the sessions listed below and linked with specific narrative, referenced, and fully illustrated. The PowerPoints and narrative will be the stimulus for discussion and the exchange of ideas - all with the aim of introducing within an historical context, Darwinian and post-Darwinian perspectives of evolutionary theory integrated with molecular perspectives enfolded within eco-evo-developmental Biology (aka the Integrated Synthesis). These PowerPoints will be information rich and a resource for further study for a time limited period after completion of the course. Hard copy written, illustrated, and referenced course materials will support your learning and understanding.
Course sessions
- Begetting Darwin: history and the social context of the evolution of evolutionary theory
We begin with a brief survey of Darwinism and then examine evolutionary thinking within the circumstances of changes in society and of society’s gradual accommodation with such thinking prior to Darwin. This history is the backdrop to our understanding of the flow of biological information from molecules to the whole living thing that helps us to begin to understand the phenotype in terms of genes and gene products ‘weaving an enchanted loom of interactions within genomes and between genomes and the environment’, to paraphrase Charles Sherrington’s famous metaphor describing the activity of the human brain.
- Development and evolution
Beginning in the 19th century, we explore the growth of the idea that embryology and development are important evidence that underpin the evolution of evolutionary theory from Darwinism to the current paradigm of the Integrated Synthesis.
- Larval Forms
The title ‘Larval Forms’ identifies the topics of the session’s content. We explore in detail the idea that types of larvae are in effect precociously hatched embryos that ancestrally were potential nodes of evolution of taxa morphologically very different from the adult stages of the juvenile forms of the life cycles described in the session.
- Galapagos Tales
Initially the history of Darwin’s finches and their influence on evolutionary theory is discussed in this session entitled ‘Galapagos Tales’. Then we take a detailed look at the long-term ecological studies that are informing current ideas about the processes that lead to speciation in the birds that are icons of evolution in action but were an enigma to Charles Darwin.
- Evo-Devo in process
Entitled ‘Evo-Devo’ in process, the session covers the developmental origins and molecular genetics of speciation with particular reference to Darwin’s finches. The session finishes with concluding remarks referring to simple fieldwork investigating speciation in a meadowland plant community local to Cambridge compared with what has been learnt about speciation in Darwin’s finches. Finally, we think of Charles Darwin as an undergraduate at Cambridge walking the meadows with his friend and mentor John Stevens Henslow, seemingly unaware of the evidence for speciation at his feet.
Learning outcomes
You are expected to gain from this series of classroom sessions a greater understanding of the subject and of the core issues and arguments central to the course.
The learning outcomes for this course are:
- an ability to contextualise the development of evolutionary theory pre-Darwin/post-Darwin, and to integrate the abundant evidence from work in developmental biology and molecular genetics that increases understanding of the processes of micro- and macro-evolution
- an appreciation of how the discovery and understanding of DNA have contributed to current evolutionary thinking, and an ability to conceptualise evolution within a multidisciplinary framework
- an understanding that phylogenetically the genetic regulation of development is highly conserved, constraining the basic body plan of metazoa to a set of components in common (not “endless forms” see On the Origin), but nonetheless enabling the dazzling biodiversity of life on Earth
- a realisation that the integration of Darwinism and Neo-Darwinism with the molecular genetics of developmental processes affirms the relevance of some of the historical ideas of evolutionary theory to current theory expressed as the Integrated Synthesis
- an appreciation of the range of evidence for evolution and an ability to summarise the evolution of evolutionary thinking
Required reading
Arthur, W, Understanding Evo-Devo, (Cambridge: Cambridge University Press, 2021)
ISBN: 9781108819466
Grant, P R, Grant B R, 40 years of Evolution: Darwin’s Finches on Daphne Major Island,
(New Jersey: Princeton University Press, 2014) ISBN: 9780691160467
Hardy, A, The Open Sea: Part 1 The World of Plankton, (London: Collins, 1956)
Kampourakis, K, Understanding Genes, (Cambridge: Cambridge University Press 2022)
ISBN: 9781108812825
It would also be to the advantage of students to view the following video resources on YouTube before the sessions indicated. Viewing after each session will help to consolidate the content of each session’s PowerPoint presentation.
Session 3: Larval Forms
What is a Veliger? CollinLabPanama, https://www.youtube.com/watch?v=xXd-sMm0G18
Bipinnarias, George von Dassow, https://www.youtube.com/watch?v=fu4_mh3KIoo
Feeding Appendicularians (Oikopleura spp.) DTU Aqua Broadcast, https://www.youtube.com/watch?v=lvX5ZqqD5GI
Understanding the behaviour of microscopic marine larvae, University of Plymouth, https://www.youtube.com/watch?v=WUzW1Xk2SFA
Session 4: Galapagos Tales
Galapagos Finch evolution HHMI BioInteractive video, https://www.youtube.com/watch?v=mcM23M-CCog
The Evolution of Darwin’s Finches on the Galapagos Islands, Harvard Museum of Natural History, https://www.youtube.com/watch?v=lQ0rJRaOV78
