The Human Pedigree: Where We Stand

Link here to a Scientific American Article.

For the past 48 hours I have been in an anthropology frame of mind. For future reference, I am posting this, based on the "Human Pedigree" article by the anthropology editor for Scientific American, Ms Kate Wong,  January, 2009, issue of Scientific American. My photocopy is hard to read, so there may be some errors, but this is how I interpret what I can make out.

The story starts seven (7) million years ago with Sahelanthropus tchadensis, first found in Chad, in 2001, and believed to be the earliest hominid.

A hominid bone of Orrorin tugenensis, believed to be six (6) million years old, has been found but it's relevance has not yet been determined. It's not part of the human pedigree. At least not yet.

Five and a half (5.5) million years ago, the first hominid ancestor appears, Ardipithecus kadabba, leading to Ardipithecus ramidus (4.5 mya) and Australopithecus anamensis (4.3 mya) and then to Lucy, Australopithecus afarensis (3.2 mya). About the same time, a contemporary, Kenyanthropus platyops (3.4 mya) appeared on the scene. The latter evolved into Homo/Kenyanthropus rudolfensis (1.8 mya) but dead-ended there. Homo/Kenyanthropus rudolfensis was a contemporary of Homo habilis, Homo ergaster, Paranthropus robustus, and Paranthropus boisei.

Lucy branched at least four times. One branch dead-ended 2.5 mya with Australopithecus garhi. Another dead-ended about the same time with Australopithecus africanus. Two branches lasted longer.  ***  One branch led to Paranthropus aethiopicus (2.4 mya) which divided into two branches, both of which dead-ended about the same time, 1.8 mya, and were noted above: Paranthropus robustus and Paranthropus boisei. Lucy's fourth branch led to Homo habilis which appears to have dead-ended 1.8 mya as a contemporary of at least three, maybe four, other hominids.

*** Australopithecus sediba, discovered in 2008, is believed to have descended from Lucy, and was a link to Homo.  In 2010, A. sediba received much press coverage as the "missing link."

However, a common ancestor (Australopithecus sediba?) after Lucy, about 2 mya branched into Homo habilis (dead-ended, as noted) and another yet unidentified ancestor (1.8 mya) divided into two branches, one leading to Homo ergaster (1.6 mya) which led to Homo antecessor (0.8 mya), then Homo heidelbergensis (0.5 mya), which ultimately branched twice, about 0.3 mya, one branch leading to Homo neanderthalensis, appearing about 100,000 years ago and dying out about 25, 000 years ago. The other branch from Homo heidelbergensis eventually evolved into Homo sapiens, appearing as a contemporary of Homo neanderthalensis, and still here today.

Much earlier, the common ancestor that branched off to Homo ergaster, also branched off to Homo erectus, appearing about 100,000 years ago, and a contemporary of Homo neanderthalensis, and possibly a contemporary of Homo sapiens.

The only other hominid in this chart is Homo floresiensis, which came from a common ancestor of Homo erectus and was also a contemporary of the Neanderthals, modern man, and Homo erectus.


Significant ancestors:

1. Sahelanthropus tshadensis: believed to be the earliest hominid (7 mya).
2. Australopithecus aferensis (Lucy): common ancestor to four branches, including the species Paranthropus and the species Homo, contemporaries.
3. Homo habilis: "handyman" -- first hominid known to have made tools.
4. Homo ergaster: the first hominid to have left Africa. 
5. Homo neanderthalensis: a big-game hunter that ruled Ice Age Europe and Asia for 200,000 years
6. Homo floseiensis: the latest surviving extinct hominid with startlingly small brain and body

On a "direct line":

Sahelanthropus tschadensis (7 mya) --> Ardipithecus kadabba (5.5 mya) --> Ardipithecus ramidus (4.5 mya) --> Australopithecus afarensis (Lucy) (3.2 mya)  --> Homo ergaster (1.8 mya) --> Homo antecessor (0.8 mya)--> Homo heidelbergensis (0.5 mya)--> Homo sapiens.

Homo habilis was  a "descendant" of Lucy, but dead-ended as a contemporary of Homo ergaster.

Homo neanderthalensis was a "descendant" of Homo heidelbergensis, but dead-ended as a contemporary of Homo sapiens.

The newly discovered hominid estimated to be about 2.5 million years old would be the common ancestor descended from Lucy and before Homo habilis; perhaps he/she is the common ancestor to the two longest-surviving species that descended from Lucy: Paranthropus and Homo.

Paranthropus (Greek for "beside" as in "along side" "human"): lived alongside Homo.

Side note: Lucy was discovered by Dr Donald Johanson in 1974. I remember that story well; I was still at an impressionable age and I was very interested in anthropology. I read his book (I still have it). In 1974 I would have been 23 years old and in my second year of medical school at the University of Southern California.