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2 results

  • 4 - Ernst Haeckel’s Evolutionary Storytelling

  • Ronald A. Jenner, Natural History Museum, London
  • Book:
    Ancestors in Evolutionary Biology
    Published online:
    08 July 2022
    Print publication:
    28 July 2022, pp 86-121

  • Summary

    In this chapter I take a detailed look at the evolutionary storytelling of Ernst Haeckel. He founded phylogenetics as the science dedicated to tracing the evolution of lineages. Although Haeckel’s phylogenetic scenarios were nourished from a broad buffet of evidence, the biogenetic law was his favorite shortcut to create lineages of hypothetical ancestors, most famously the tiny cup-shaped Gastraea. A recent consensus has emerged that stigmatizes Haeckel’s phylogenies as unDarwinian constructs that are conceptually stained by teleological thinking and the linearity of the scala naturae. Instead, I argue that his trees are fully Darwinian, and that the linearity present in his trees and thinking is the linearity of evolving lineages that track the arrow of time. Lineage thinking was novel when Haeckel started writing, and his was marred by imperfections. It was up to the following generations of evolutionists to resolve the conceptual tension between the linear and branching aspects of evolution, a struggle that is still ongoing in today’s literature.

  • Structural synthesis of maximally regular T3R2-type parallel robots via theory of linear transformations and evolutionary morphology

  • G. Gogu
  • Journal:
    Robotica / Volume 27 / Issue 1 / January 2009
    Published online by Cambridge University Press:
    01 January 2009, pp. 79-101

  • The paper presents structural synthesis of maximally regular T3R2-type parallel robotic manipulators (PMs) with five degrees of freedom. The moving platform has three independent translations (T3) and two rotations (R2). A method is proposed for structural synthesis of maximally regular T3R2-type PMs based on the theory of linear transformations and evolutionary morphology. A one-to-one correspondence exists between the actuated joint velocity space and the external velocity space of the moving platform. The Jacobian matrix mapping the two vector spaces of maximally regular T3R2-type PMs presented in this paper is the 5×5 identity matrix throughout the entire workspace. The condition number and the determinant of the Jacobian matrix being equal to one, the manipulator performs very well with regard to force and motion transmission capabilities. Kinematic analysis of maximally regular parallel robots is trivial and no computation is required for real-time control. This paper presents in a unified approach the structural synthesis of PMs with five degrees of freedom with decoupled and uncoupled motions, along with the maximally regular solutions.