Roots

To my way of thinking, when it comes to determining our roots

there are three classes of researchers – the diggers, the daters and

the DNAers. The diggers are those who go out to these remote

places and painstakingly chip and brush and carefully retrieve the

remains of various species, as well as any tools or other artifacts.

In many cases, the diggers will have some ideas as to the dates of

the findings just from the location in the layers of rock laid down

over the ages or from the fact that particular objects are retrieved

from soil lying under an earlier civilization.

Today, there are other methods of dating, carbon dating being

perhaps the best known of the techniques. Other methods may

employ the amounts of certain radioactive elements or the ratios

of various isotopes of certain elements. The “daters” generally

can operate in the comfort of their laboratories by analyzing the

samples obtained by the diggers. Of course there are those who

are both daters and diggers. An example is Sue, one of my

nieces. Sue has been involved in the dating of the Shroud of

Turin but also has traveled on ships in the Southern Hemisphere

collecting samples of coral from the sea bottom.

The third group, the DNAers, uses DNA to trace the evolution

and wanderings of various species. Back in the late 1980s one

group of DNAers published a study that created quite a fuss. The

study, by Rebecca Cann and her coworkers, involved comparing

the mitochondrial DNA, mtDNA for short, in women having

ancestries that spanned the world. Their results led them to

postulate that we Homo sapiens could trace our ancestry back to

an African “Eve” who lived about 140,000 to 290,000 years ago.

Let”s digress a bit for those of us who don”t or didn”t know (that”s

me) what mtDNA is and why one might be presumptuous enough

to think we could use it to determine our ultimate grandmother.

First, what are mitochondria? And, didn”t we talk just a couple

weeks ago about DNA being in the nucleus of a cell? The

mitochondria are little structures that lie in cells outside the

nucleus, but inside the cell wall or membrane. These

mitochondria are pretty important since they handle the energy

processes going on in our cells. Mitochondria that aren”t properly

constructed can also cause various diseases. It turns out that the

mitochondria contain some DNA that lies outside the nucleus and

hence, as I understand it, is not part of the 23 chromosomes that

have been decoded in the human genome.

The history of mitochondria is rather strange, too. You”ve all

seen or heard of cases where large predatory land or sea animals

allow much smaller creatures such as birds or small fish to

perform tasks that benefit the larger animal. For example, small

birds might pick off insects or otherwise tidy up material that

annoys a rhinoceros or a crocodile. Other smaller creatures might

provide or attract food for their host. Well, current thinking is

that billions of years ago, some bacteria managed to either invade

or be engulfed by some cells. It is presumed that the bacteria

turned out to perform some kind of useful function and the

symbiotic arrangement between the cells and the bacteria

endured. The bacteria, in a modified form, are now the

mitochondria containing the DNA originating from the bacteria.

What makes the mtDNA special is that, unlike the DNA in the

nucleus, the mtDNA does not have a contribution from the father

but only the mother (however, see later). Another feature of the

mtDNA is that the DNA tends to change or mutate at a faster rate

than the nuclear DNA. It is the rate of mutation that was used in

the mtDNA work to essentially extrapolate backwards to our

ancestral “Eve”. I”m not privy to exactly how this extrapolation

was done.

Now, anthropologists and archaeologists are quite a contentious

lot and immediately there was a lot of skepticism about the

mtDNA work. The criticisms ranged from concerns about such

things as the sampling and the computerized treatment of the

data. In the intervening decade or so, the controversy has not

abated and now there is a new factor that has been thrown into

the pot. There is now evidence that some paternal DNA can

enter the mitochondria, at least on rare occasions. This of course

throws a monkey wrench into the assumption of a certain

mutation rate extending back in time. At the same time, there are

those who claim not to have found any evidence of any paternal

contribution to the mtDNA in families, where you might expect

evidence of paternity entering in. Studies are underway to find

the original “Adam” by studying the Y-chromosome, which has

only contributions from the father.

While all this controversy goes on, the diggers keep digging and

the daters keep dating. I happen to be one of those individuals

funding some of these digs. Ok, I confess that it”s probably only a

few cents, if that, per year through my subscription to National

Geographic. (Do you also have the same problem we have of

hating to throw out any of decades” worth of Geographics?) The

National Geographic Society funds many archaeological digs and

always has the greatest pictures in their articles. In the July issue,

I was taken with an article by Rick Gore entitled “People Like

Us”, dealing with the dawn of the thinking and creative Homo

sapiens, us modern types.

Over the years I”ve read all kinds of articles on the evolution of

Homo sapiens. The prevailing theories of our roots and the

spread of our modern brand of primate around the world have

undergone many revisions. For the most part, the revisions have

come about thanks to the work of the diggers and daters. For

example, up until recently, the prevailing opinion was that the

settling of North and South America was accomplished by

adventurous characters from Siberia walking across the frozen

Bering Strait somewhere around 12,000 years or so ago. These

people and their heirs then were presumed to gradually penetrate

inland and migrate over generations down into South America

eventually populate the Western Hemisphere.

Now the diggers have unearthed sites that put humans in Chile

over 12,500 years ago. This led to the proposal that there was a

colonization parallel to the walkers that took place by people who

used boats to skirt and settle along the coasts of North and South

America. Furthermore, digs in the eastern United States, even

near Pittsburgh where I did my graduate work, has yielded what

could be important information. These sites show signs of a

possible European influence way before the Vikings are now

thought to have made their expeditions to North America. The

same sort of thing has happened in Brazil, where reconstructed

facial features of fossil remains don”t appear to resemble the

American Indian but may indicate an Australian connection. Thor

Heyerdahl, of Kon Tiki fame, postulated such a migration across

the South Pacific many years ago but it has apparently been pretty

much ignored as a viable hypothesis.

The above paragraph is based mostly on an article in the New

York Times Science Times of November 9, 1999. The National

Geographic article is broader in scope, trying to track down

Homo sapiens” earliest origins. Our Western Hemisphere

colonizers were relative newcomers to the scene compared to the

original settlers of Australia, for example. Take the case of the

Mungo Lady. This poor gal died in her 20s. After her death, her

body was placed on a funeral pyre and her charred bones were

smashed before being placed in a hole in a dune field. She

remained there until discovered in 1968. Initially, her bones were

dated at 24,000 years and now her bones are in a vault at the

Mungo National Park headquarters. The Aborigines care for her

and treat Lady Mungo as a symbol of their heritage, coming out

of the ground to guide them.

It happens that the Lady is not only guiding the Aborigines but

also all of us. The daters have taken another look at her and now,

using three different methods, have come up with a revised figure

of about 62,000 years! Why the exclamation point? This puts the

Mungo Lady in Australia some 30,000 years ahead of the first

fossils of the Cro-Magnon in Europe. The Cro-Magnon, named

after the location in France where the fossils were first found,

were the first of the Homo species to exhibit modern behavior in

Europe. The Mungo Lady therefore was an affront to the

common assumption that humans spread to Europe before

spreading eastward to Asia and then South Pacific. I would be

remiss if I didn”t mention that the 62,000-year date is still

controversial in spite of the three different dating techniques.

Although everything points to Homo sapiens arising out of

Africa, there wasn”t much evidence of modern behavior there

before the evidence found in Europe, or now in Australia.

However, this changed in quite a spectacular manner when the

diggers, or perhaps I should call them spelunkers, investigated

Blombos Cave at the southern tip of South Africa. In Blombos

Cave they found one of the accepted indications of modern

human behavior, the presence of bone tools such as awls and

possibly spearheads. The daters believe this site to be over

70,000 years old. Now we”re getting there! Another telling

finding was the presence in the cave of fish bones, including some

from a sizeable fish called a black musselcracker, still in the area

today. The hypothesis is that the inhabitants of Blombos Cave

had figured out how to attract and spear the fish and that this in

turn implies an ability to share information through language. If

all this stands the scrutiny of the scientific community, “Out of

Africa” is certainly more than the title of a good book or movie,

it”s people like us!

Meanwhile, the diggers and daters and DNAers continue their

work. Someday, the three groups might come together in

harmony and there won”t be any controversy. But then that

wouldn”t be any fun, would it? Is it perverse of me to think of all

this as being like a hockey game? The only shots you see on TV

on the nightly sports segments, are the scoring of the goals by the

Gretzkys of the game. But most of the action is by the diggers at

the two ends of the rink, down and dirty, trying to get that puck

out of danger and back up the ice for the scorers to get a chance.

Allen F. Bortrum