A present-day view of evolutionary theory Vidyanand Nanjundiah Centre for Human Genetics Bangalore Indian National Science Academy, Delhi 3 November 2014

The problem To account for the presence on earth of the highly improbable forms of matter known as living creatures

( Living Matter

Clue: the forms of living matter are interrelated Principle of continuity

Vertebrate forelimbs

The answers 1.Principles of physics and chemistry. 2.Chance. 3.Natural selection.

The answers 1.Principles of physics and chemistry. Ahistorical 1.Chance. 2.Natural selection.

D’Arcy Thompson, “On Growth and Form”

and

and

The answers 1.Principles of physics and chemistry. 2.Chance. Ahistorical: accidents whose outcomes persisted; ‘random walk’ 1.Natural selection.

(cytochrome C) evolution-north.html

Luidia sarsi (zygote develops into juvenile starfish with radial symmetry inside a larva with bilateral symmetry; Williamson & Vickers, Am Sci 95(6): , 2007)

The answers 1.Principles of physics and chemistry. 2.Chance. 3.Natural selection. Historical: accidents, advantageous outcomes; ‘biased random walk’

Alfred Russel Wallace ( )

Why does natural selection occur? Because the individuals of a species are not all alike; because they differ in their ability to survive and reproduce; because they can pass on these traits to their children. These are testable statements!

Genes and Organisms Genes  Proteins  Organelles  Cells   Tissues  Organisms

The essence of neo-Darwinian theory 1.Living organisms carry DNA or RNA sequences (genes) that can be copied inside a cell. The sequences differ from one individual to another. 2.Genes specify proteins. 3.Proteins ‘build’ bodies and confer various properties on organisms. 4..Some individuals leave behind more children than others because they have different properties. 5.Then the protein composition of a population, and so also the genetic composition, changes in time.

Environmental pressure: relative, external Genetic variation: random, internal Response: systemic, internal

We cannot run faster than him!

I don't want to run faster than him; I want to run faster than YOU !

The signature of natural selection: Adaptation (

Does the neo-Darwinian framework require modification? Do many roads lead to Rome?

Heritable variation without genes: epigenetic inheritance Ciliary row pattern in Tetrahymena (

Environment created by organism: Niche construction snailstales.blogspot.com

Egyptian plover and Nile crocodile ( Co-evolution

Variation dependent on the environment: phenotypic plasticity

Environment-induced modification Daphnia;

Self-organisation R. Blanton

Scope of evolutionary thinking : 1.Mathematics 2.History 3.Culture 4.Behaviour 5.Psychology

What next?

Echinoidea; Van Valen, L Evol. Theory 1: 1-30.

Summing up

Following slides ‘extras’, to be used only if the subject crops up during question time

What next?

The brain

Evolution is also concerned with dead matter

Vertebrate forelimbs

‘Plasticity’

Phenotypic plasticity (PANC-1 cells express FGF-2 (red) or FGF-2 receptor (green), but not both) Hardikar et al. (2003) PNAS 100(12): 7117–7122

Spontaneous self-organisation

Life cycle of slime mould

Reproduction “1  1+1” “1  1/2”

Asexual reproduction (mitosis): 1  1+1

Sexual reproduction (meiosis): 1  1/2

Molecular biology applied to evolutionary questions

Behaviour too has evolved

The nerve cell

Natural selection can be compared to climbing Getting to the next peak involves crossing a valley

OK, I'll try to divert him. And you'll see, my genes can spread better than yours!

The signature of natural selection: Adaptation Adaptation works only in the short term. Natural selection has no way of planning for the long term.

Natural selection Natural selection depends on particular properties of living matter: Variation Almost faithful reproduction Differences in ability to survive and reproduce