Evolution through Natural Selection: the growth of an idea

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’
• equip you with an understanding of techniques and the terminology that helps you to engage in conversations affecting society’s perception of modern evolutionary science

Content

Evolutionary theory within the context of molecules to ecosystems will be covered with an historical perspective that highlights ‘Evolution through Natural Selection: the growth of an idea’.

For Darwin, comparative embryology was important evidence in support of the evolution of descendants from a common ancestor. In 1874, the German biologist Ernst Haeckel followed Darwin’s line of thinking with the notion that ancestral developmental processes are repeated during embryonic development, and are a record of evolutionary ancestry, ‘ontogeny (embryonic development) recapitulates phylogeny (evolutionary history)’, the biogenetic law that dominated evolutionary thinking in the late 19th century.

Walter Garstang at Leeds University highlighted the problems of recapitulation theory 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 precociously hatched embryos. Subject to Darwinian selection, larvae are potentially the nodes for major evolutionary innovation as the result of selection of larval characteristics consequently affecting adult morphology/physiology in subsequent generations. 

Developmental changes and their genetic regulation that might be the node (starting point) for the evolution of new taxa perhaps prompt a re-definition of evolution as: a modification of ontogeny (development) as the result of changes in gene regulation (where/when/how much gene product), rather than: a change in gene frequency in a population, a central idea in the Neo-Darwinian synthesis dominant in evolutionary thinking from the 1920s to the 1980s. And accumulating molecular evidence is highlighting the influence of the epigenome on gene expression. These epigenetic effects can be inherited. Do these findings revive questions about the inheritance of acquired characteristics? The growth of an idea indeed.

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 techniques of molecular genetics. For example, Arkhat Abzhanov at Imperial College, UK et al have unravelled with colleagues the intricacies of the genetic interactions controlling beak development in Darwin’s finches, deepening our understanding of how new finch species/sub-species have evolved from a common ancestor arriving on the islands from South America about two million years ago. 

Evolutionary-developmental biology (evo-devo) highlights how the interactions between genes and their products might affect the micro-evolution (see ‘Galapagos Tales’) and macro-evolution of lineages (see ‘Larval Forms’). Today, the emerging discipline reframes the arguments of earlier evolutionary thinking, adding molecular biology to our understanding of how molecular and developmental processes influence evolution. The sessions explore a synthesis of these ideas to reassess the nature of evolution in process.

Presentation of the course 

The course will include fully illustrated lectures, each PowerPoint with linked specific narrative; led Group Discussion; exchanging ideas; case studies; all with the aim of introducing innovative perspectives on Evolutionary Theory. Written, illustrated and referenced course materials support your learning and understanding.

Course sessions

1. 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. 
2. 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. 
3. 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.
4. 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.
5. 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=lvX5ZqqD5G

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

Typical week: Monday to Friday 

Courses run from Monday to Friday. For each week of study, you select a morning (Am) course and an afternoon (Pm) course. The maximum class size is 25 students.   

Courses are complemented by a series of daily plenary lectures, exploring new ideas in a wide range of disciplines. To add to your learning experience, we are also planning additional evening talks and events. 

Evaluation and Academic Credit  

If you are seeking to enhance your own study experience, or earn academic credit from your Cambridge Summer Programme studies at your home institution, you can submit written work for assessment for one or more of your courses.  

Essay questions are set and assessed against the University of Cambridge standard by your Course Director, a list of essay questions can be found in the Course Materials. Essays are submitted two weeks after the end of each course, so those studying for multiple weeks need to plan their time accordingly. There is an evaluation fee of £75 per essay. 

For more information about writing essays see Evaluation and Academic Credit. 

Certificate of attendance 

A certificate of attendance will be sent to you electronically after the programme.