Skip to main content Accessibility help
×
Home
Hostname: page-component-5959bf8d4d-kpqxq Total loading time: 0.389 Render date: 2022-12-08T18:01:10.171Z Has data issue: true Feature Flags: { "useRatesEcommerce": false } hasContentIssue true

1 - March of the Bipeds: The Early Years

from PART I - TEETH AND AUSTRALOPITHS

Published online by Cambridge University Press:  05 August 2016

Debbie Guatelli-Steinberg
Affiliation:
Ohio State University
Get access

Summary

It is, however, very difficult to establish the precise lines of descent, termed phylogenies, for most organisms.

– Ayala FJ and Valentine JW Evolving: The Theory and Process of Organic Evolution (7)

As understood today, human evolutionary history involves some twenty species of fossil hominins, give or take a few depending on the taxonomic scheme to which one subscribes. In the field of paleoanthropology, taxonomic questions – how to classify fossil species – are famously contentious. As Richard Dawkins comments in the Ancestor's Tale (8), there is more than one paleontology book in print entitled “Bones of Contention.” Names given to species carry implications for how species are related to one another. A species placed in the genus Homo for example, is recognized as sharing a more recent common ancestor with modern humans than a species placed in the genus Australopithecus.

Resolving species relationships is no straightforward task. That is one reason (among others) why there are so many different points of view about evolutionary relationships among hominin species. Such relationships are summarized in diagrams called phylogenies or phylogenetic trees. All methods of constructing phylogenies rely on comparing the characteristics of species, from their DNA sequences to their dental features to any aspect of their anatomy and even behavior. The most direct means of genetic comparison is through DNA, but, only in more recent hominins has it thus far been possible to extract adequately preserved DNA (see Chapter 5). For earlier species, the characteristics of teeth and bones must suffice for assessing evolutionary relationships. As noted, teeth figure prominently in such assessments: they are extremely well-preserved in the fossil record and much of the variation in their morphology is due to genes (rather than environment).

There are different ways to assess evolutionary relationships among species. According to the method of phenetics, all available traits should be used to construct phylogenies. Species with greater similarity are considered more closely related. This method does not take into account two big problems. The first is the problem of homoplasy, when two species have similar traits but not because they inherited them from a common ancestor. One way that homoplasy can occur is when species independently evolve similar solutions to similar problems. The wings of dragonflies and seagulls were not inherited from their common ancestor but evolved independently as adaptations for flight in their separately evolving lineages.

Type
Chapter
Information
Publisher: Cambridge University Press
Print publication year: 2016

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

Save book to Kindle

To save this book to your Kindle, first ensure coreplatform@cambridge.org is added to your Approved Personal Document E-mail List under your Personal Document Settings on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part of your Kindle email address below. Find out more about saving to your Kindle.

Note you can select to save to either the @free.kindle.com or @kindle.com variations. ‘@free.kindle.com’ emails are free but can only be saved to your device when it is connected to wi-fi. ‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.

Find out more about the Kindle Personal Document Service.

Available formats
×

Save book to Dropbox

To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Dropbox.

Available formats
×

Save book to Google Drive

To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Google Drive.

Available formats
×