The Descent of Man - Notes

PREFACE TO THE SECOND EDITION

  • Correlated growth implies that the variation in one part of the organism can affect others, leading to modifications through selection. Critics suggested sexual selection was invented to explain structures natural selection couldn't; however, the principle was outlined in the first edition of 'Origin of Species' and is now expanded because of available opportunities.
  • Conviction of sexual selection's power remains, although some conclusions may be erroneous. As naturalists become more familiar with sexual selection, it will gain broader acceptance.

INTRODUCTION

  • Notes on the origin of man were collected over many years without intention to publish, due to anticipated prejudices.
  • The 'Origin of Species' implied man's inclusion in general conclusions about organic beings' appearance on Earth.
  • Carl Vogt stated most naturalists admit species are modified descendants of other species, especially among younger naturalists who accept natural selection, though its importance is debated.
  • Notes were compiled to assess applicability of former works' general conclusions to man. Focus on a single species means losing arguments from the affinities connecting organism groups, geographic distribution, and geological succession.
  • Homological structure, embryological development, and rudimentary organs remain for consideration, providing evidence for gradual evolution.
  • The work's objectives include:
    • Determining if man descended from a pre-existing form.
    • Understanding the manner of man's development.
    • Assessing the value of differences between human races.
  • The book will not detail differences between races because it has been fully discussed already
  • High antiquity of man, demonstrated by scientists since Boucher de Perthes, is taken as the basis
  • Amount of difference between man and anthropomorphous apes will not be discussed beyond Huxley's conclusive showing that man differs less from higher apes than they do from lower primates.
  • The work contains few original facts, but arrived conclusions may be interesting to others. It's been confidently asserted that man's origin cannot be known, but ignorance is the base of confidence.
  • Lamarck's conclusion that man shares common descent with other species is supported by Wallace, Huxley, Lyell, Vogt, Lubbock, Büchner, Rolle, and especially Haeckel.
  • Haeckel's 'Natürliche Schöpfungsgeschichte' (1868) discusses human genealogy and confirms nearly all conclusions in the essay.
  • Sexual selection is considered important in differentiating human races. Application to man requires full treatment of the subject.

PART I: THE DESCENT OR ORIGIN OF MAN

CHAPTER I: THE EVIDENCE OF THE DESCENT OF MAN FROM SOME LOWER FORM

  • To assess whether man descended from a pre-existing form we must consider:
    • Variations in bodily structure and mental faculties transmitted to offspring based on laws prevailing with lower animals.
    • Whether variations result from similar causes and are governed by the same laws as in other organisms.
    • Whether man is subject to similar malformations and displays reversion to ancient structure types.
    • Whether man has given rise to varieties/sub-races or races differing so much they're doubtful species; and if so, how are they distributed, react upon crossing, etc.
    • Tendency to increase at a high rate, leading to a struggle for existence; whether favorable variations are preserved, and whether races encroach, with some becoming extinct.
  • Bodily Structure:
    • Consistently constructed like other mammals; skeleton comparable bone-for-bone.
      • Muscles, nerves, blood-vessels, and internal organs are very similar to other mammals.
    • Brain follows the same law, as per Huxley; brain shows analogy to the orangutan, but differences remain and perfect agreement cannot be expected.
    • Vulpian remarks that real differences between the human brain and that of apes are minimal; man is closely related to anthropomorphic apes, even more than they are to certain other primates.
  • Similarities not directly connected with structure:
    • Susceptibility to the same diseases from lower animals (hydrophobia, variola, glanders, syphilis, cholera, herpes) proves close similarity in tissues and blood.
    • Monkeys share non-contagious diseases with humans (catarrh, apoplexy, bowel inflammation, cataract); medicines have the same effect.
    • Monkeys have tastes for tea, coffee, liquors, and tobacco, implying nerve similarity.
    • Baboons captured via strong beer, exhibit drunkenness, and suffer hangovers, craving lemons rather than alcohol the next day.
    • Monkey’s aversion to brandy after drunkenness shows similar neural taste responses to humans.
    • Man is infested by the same genera/families of internal/external parasites as mammals; scabies affects both.
    • Subject to the same lunar-period law for gestation, maturation, and disease duration; wounds heal similarly; amputated stumps may regenerate as in lower animals.
    • Reproduction strikingly similar from courtship to nurturing young. Monkey infants are as helpless as human infants; some genera’ young differ from adults like human children do from parents.
    • Human immaturity is not much later than orangutans in tropical countries.
    • Man, like mammals, expresses differences between sexes in size, hair, mind, and body.
    • General structure, composition, and constitution similarities exist between humans and apes.
  • Embryonic Development:
    • Developed from ovule like other mammals. Embryo is indistinguishable early on from other vertebrates.
    • Embryos have branch-like marks with arch-like shapes carrying blood like gills of fishes which are present in some high vertebrate animals.
    • Extremities of lizards and mammals arise from the same fundamental form; early human resembles young ape, diverging later.
    • At later development stages the embryo resembles certian low-level life forms.
    • The heart is initially a pulsating vessel and excreta is voided through a cloacal passage, coccyx projects in tail-like manner.
    • Embryos of air breathers have corpus Wolffiana corresponding to kidneys of mature fishes. Bischoff notes human fetal brain convolutions at seven months mirror adult baboons.
    • Professor Owen notes that the great toe's structure is a characteristic of humans, however a one-inch embryo shows that the great toe projects to the side demonstrating the quadrumana structure of the foot.
    • Embryotic origins and early development is identical to animals below on the scale of evolution, closer resemblence to apes than apes to dogs.
  • Subject will be treated more fully because it is important to understand that animals can bear rudimentary conditions; Man is no exception to the rule.
    • Rudimentary organs must be distinguished from those that are nascent; the former are useless (male quadruped's mams) or of slight use. Organs in the latter state are not truly rudimentary, but are trending that way. Nascent organs while not fully developed, are of high service.
    • Rudimentary organs are variable due to uselessness removes from natural selection leading to complete suppression. They are also liable to reappearance through reversion.
    • Chief cause of organs becoming rudimentary:
      • Disuse during period of life when the organ is most used (maturity).
      • Inheritance.
      • Reduced blood-flow to a part or organ from fewer pressure alternations or less habitual activity.
    • Rudiments occur in one sex when normally present in the other, these originate distinctly.
    • Natural selection reduces organs harmful to species with changed habits.
    • Reduction aided by compensation and growth economy; suppression is difficult to understand.
    • Final suppression in useless parts has been explained by Pangenesis.

Correlated Variation

  • Structures intimately related: when one part varies, so does another (due to I. Geoffroy's findings); homologous structures change together across body sides.
  • Meckel notes that when arm muscles deviate, they mimic leg muscles, and vice versa.
  • Sight/hearing organs, teeth/hair, skin/hair color, and color/constitution are correlated.
    Professor Schaaffhausen: stronger frames link to pronounced supra-orbital ridges in lower races of man. Additionally some variations may be called spontaneous that arise without an exciting cause.

Rate of Increase

  • Civilized populations can double in 25 years; Euler calculated this could occur in 12 years.
  • With that rate the globle would be covered by humans in 659 years.
  • Primary check to a continued increase is the difficulty of gaining subsistences.
  • Affirmed by the US, easy subsistence and plenty of room
  • Doubling subsistence would double #s in brittain.
  • This effect is restrained by marriage restraint.
  • Greater infant mortality is a large population deterrent
  • Epidemics and wars are soon countered due to favorable conditions for those placed in respective conditions.
  • Emigration is a temporary check, however is not great with the extremly poor classes.
  • Malthus remarked there is suspicion that reproduction is less prolific in barbaric than civilized and this is shown by small families with missionaries.
  • Savages may suffer much and lack nutritious food, making them less prolific; domestication of crops, birds, and quadrupeds prove they are more fertile is proof of the previous argument.
  • Men who are civilized are expected to be highly domesticated and more prolific, this also could pass on via an inherited trait.
  • Savages almost always marry, young men are often required to show support by earning a price for their wife, difficulty in obtaining materials is also a deterent.
  • Tribes can undergo dire famines that injure the population
  • As was assured by Australia, Savage tribes fluctuate with extreme reasons and are usually at war with any neighbors.

Natural Selection

  • Here it's been seen that man is variable in mind and body and that the variations directly/indirectly follow the same causes and laws as with mammals. Early Progenitors like all the other animals would have faced times where there was great struggle for the daily subsitence.
  • Beneficia variations of alk kinds preserved, injurious were eliminated. The muscles provide the range of movement that an animal has.
  • The race that is fittest for gaining subsistence or defending will likely pass on more offspring.
  • Man is the mos dominant animal on the planet due to
    • Intellectual faculties
    • Social habits
    • Corporeal structure
  • Powers of inellect have enabled articule language and helped all advancement.
  • Direct resutls of observation, imagination, curiosity and reason have given tools to fight off anything whether animal or envroment.
  • Natural selection could only have endown the savage with sligh brain advantage.

Part SECTION XVIII:

  • Summary: Throughout the mammal class the law of battle is the source of dominance and can show strength and courage, can also modify selection that is called sexual, this is typically greater amongst a male who becomes successful
  • The second class of struggle is between allure and excitemnt, there can be several charms that make this a reality, for instance odourous glands that have been acquired through sexual selection.
  • Crests, tufts and martials of hair are confined to a male setting or are developed more. However the branching horns typically server as an ofence or defence. When colouration differs amongst the sexes it almost always stronger amongst the males.

Part XVIII:

  • Chapter 19: With mankind the differences with the sexes greater than most Quadrumana, man is usually taller and stonger, women slightly shorter and less physically gifted, in some cultures the difference in tone varies quite vastly. The faces are rounder for women and their pelvis is bronder
  • With respect to mental capability:
    • Man is courageous and more inventive
    • Women are more maternal in mind
  • The beard, wiskers or moustache never grow in women but grow much more in men. In most races men's beard is usually lighter than the rest of their head. Women in races that exist on earth are usually less hairy
  • Races that are brave lead and will always come to the front in the face of danger. From the facts shown above it's seen that many similarities exist from men to Quadrumana however those of the baboon and orangutan differ far more