Submitted by Sammy Smith ([email protected])

Figure 1 from Wood’s paper, “Reconstructing human evolution: Achievements, challenges, and opportunities.” His caption is in the main text below.

Read summaries of the latest scientific studies and analysis of evolution in human beings. The Proceedings of the National Academy of Sciences of the United States of America, commonly called PNAS, have a full issue titled In the Light of Evolution IV: The human condition, dated 11 May 2010. Papers from the colloquium are available online for free. The colloquium was held in December 2009. The speaker list and links to audio downloads of the presentations is here.

The first paper, “Reconstructing human evolution: Achievements, challenges, and opportunities,” by Bernard Wood, who is trained as a physician and as a paleoanthropologist. The paper begins:

This contribution begins by considering two achievements relevant to reconstructing human evolution: resolving the branching structure of the higher primate part of the tree of life and the recovery of a substantial body of fossil evidence for human evolution (Fig. 1). The second part considers some of the challenges faced by those who try to interpret the taxonomy and systematics of the human fossil record.

Wood’s Figure 1 is shown above. His caption reads:

Taxa recognized in a typical speciose hominin taxonomy. Note that the height of the columns reflects either uncertainties about the temporal age of a taxon, or in cases where there are well-dated horizons at several sites it reflects current evidence about the earliest (called the first appearance datum, or FAD) and the most recent (called the last appearance datum, or LAD) fossil evidence of any particular hominin taxon. However, the time between the FAD and the LAD is likely to be represent the minimum time span of a taxon, because it is highly unlikely that the fossil record of a taxon, and particularly the relatively sparse fossil records of early hominin taxa, include the earliest and most recent fossil evidence of a taxon. The newest archaic hominin taxon, the ca.1.9 Ma Australopithecus sediba, would occupy the space just above the box for Au. africanus.

Let’s decode a bit…. Hominin refers to species within the same genus as human beings, the genus Homo. No other living species are taxonomically categorized with us in the genus Homo. Taxonomy refers to a hierarchical classification system, in this case the scientific classification of organisms (or once living things, in the case of many fossils). A taxon is a set of organisms that taxonomists have lumped together.

So, Wood’s Figure 1 portrays his interpretation of species in the genus Homo plotted against a timeline. The bottom of the figure is oldest and the top is newest. Each bar is plotted with its vertical length portraying the duration of that species, as is presently understood. In the paper, he discusses the data he uses in this reconstruction, and the assumptions he has made to produce it. Thus, he presents sufficient data for you to make your own version of Figure 1, if you choose to make different assumptions.

We also have discussed taxonomies elsewhere on this website.

Each year, the National Academy of Sciences schedules four to six Arthur M. Sackler Colloquia. They address scientific topics of broad and current interest, cutting across the boundaries of traditional disciplines. These colloquia are funded by a generous gift from Jill Sackler, in memory of her husband, Arthur M. Sackler.

Posted online on Friday, May 21st, 2010