The January 2001 issue of Discover magazine was particularly
interesting and has provided the impetus for several recent
columns. I was about to file the magazine when I saw all the
commotion on TV about those adopted twins and the problem of
the birth mother wanting to regain her children. This reminded
me of an article in that Discover issue by Evan Eisenberg,
himself an adoptive parent. The article is titled “The Adoption
Paradox” and raises the question as to how the adoptive process
squares with prevailing notions of evolutionary theory. You
often read or hear that the prime objective of a species is to
perpetuate itself. On an individual basis, this means doing your
best to pass along your genes to a succeeding generation.
Adoption seems contradictory to this objective since it obviously
involves raising a child having no genetic ties to the parent(s).
Certainly, in the case of the human species, I understand the
desire to have children and it seems to me the bonding with an
adopted child can be as strong and as satisfying as with a child
related by birth. The article goes into considerable detail
examining the history and various aspects of adoption. What
really intrigued me were the examples cited in the article about
adoption, or its equivalent, in nonhuman species. Much of the
time, adoption is not a voluntary process but comes about
through deception by another member of the species. One
famous example is that of the cuckoo. The cuckoo is roundly
castigated for taking advantage of the absence of the parents
from the nests of birds of another species. The cuckoo lays an
egg in the nest along side the other eggs and the poor parent birds
come home not knowing they”ve been had. Of course, the larger
cuckoo hatchling gets the biggest share of the worms or whatever
and the smaller chicks suffer and may die of starvation or being
kicked out of the nest by the larger cuckoo.
I hadn”t realized that this practice was more widespread than the
cuckoo and also the cowbird. Bluebirds also engage in this
practice. However, they stick to their own kind and lay eggs in
other bluebirds” nests. The bluebird females of the invaded nests
don”t take kindly to this tactic if they detect the perpetrator in the
act. One study found that 15 percent of the bluebird nests in the
study contained unrelated bluebird eggs. Cliff swallows out
West not only lay eggs in their neighboring cliff swallows” nests
but even go to the trouble of carrying eggs from their own nest to
another one. The cliff swallows don”t put up any fuss over this
invasion of their nests because they probably have done the same
thing. For the swallows, the mixing of the eggs may be a form of
insurance. The swallows” nests are rather precariously located
where they can be battered by rockslides and storms, etc. If
you”re a swallow, it may make sense to spread your eggs as
widely as possible to assure that some of your progeny survive.
Now an egg is a pretty immobile object and doesn”t have any
choice where it ends up. On one of our New York TV stations
the nightly news features a segment on Wednesday called
“Wednesday”s Child”. A selected child is profiled in hopes that
he or she will be adopted. If adopted, the child had no real role
in selecting the adoptive parents. In the bird world, there are
some exceptions. These occur in cases where the birds live in
tightly packed colonies. In one study, some white stork chicks
were found to desert an overcrowded nest and wander around to
another nest with fewer and typically, younger, chicks. Although
the parents would object, they would eventually give in and
support the interloper. The chick would end up profiting since it
would be better fed than back in its own nest.
As mentioned, bluebird females fight the intrusion of an extra
mouth to feed pretty briskly if they know about it. Yet ducks and
geese tend to be more placid about one more kid to handle. It is
thought that the energy devoted to feeding is a factor. The
bluebird works like a dog to feed its nestlings. The author of the
article likened it to a human chopping wood day and night. On
the other hand, young ducks and geese learn to forage for
themselves pretty quickly after hatching, so it”s not that much of
a strain on the parents to have an extra youngster in the fold.
An oddity is the herring gull female. If she stumbles upon
another herring gull mother”s chick, she”s not averse to taking the
chick home with her and eating it. Once in awhile, however, if
she gets to the nest and the chick is still alive, clamped in her
beak, she might decide to start feeding it as one of her own. The
speculation is that she has a “senior moment” and forgets
whether the live chick was brought home for dinner or whether
the chick is one of her own that had strayed from the homestead
and she was just bringing it back. Not wanting to be accused of
eating her own chick, she adopts the item she”d planned for
dinner. I can certainly empathize with the senior moment bit.
Voluntary or involuntary adoption is not all that rare among
mammals and birds. When you see the pictures of seal breeding
grounds with thousands of seals all jammed together on this
island, you may wonder how the mothers keep track of their
offspring. In some cases, they don”t. Instead they”ll pick up
another pup to take care of and nurture. Sometimes, a female
who has not given birth at all will adopt a pup. In general,
mammals and birds don”t have too many offspring and they
spend a lot of time and effort feeding their kids.
With fish it”s a different story and adoption is quite common. A
fish may lay thousands or zillions of eggs and hope that at least a
few survive. If some other fish”s eggs get mixed in, it”s no big
deal and actually may be a good thing. The more eggs there are,
the less chance that its own eggs will get eaten. This dilution
effect can be enhanced. If the adopted fry are smaller and more
vulnerable, the predator will eat them first. In some cases, the
adopted fry are placed on the outer fringes of the brood, making
them more vulnerable to attack. Either way, the related fry have
a better chance of survival.
Even worms may adopt. There”s a species of marine worms that
lay their eggs in communal nurseries. The worm parents care for
their own eggs but a single, unattached worm may adopt any
neglected eggs. That worm isn”t polishing those eggs out of
compassion for the kids. Mating takes place in the nursery and
this dude is just hanging out looking for a mate. As Eisenberg
puts it, he”s using the nursery as a singles bar!
When it comes to our primate cousins, the desire to nurture is so
strong that some female apes will take in orphans or even resort
to kidnapping if an orphan is unavailable. On the other hand,
some males will adopt for more selfish reasons. A male
macaque may adopt an infant to shield himself from attack, while
a hamadryas baboon may adopt a young female over the protests
of the mother. The baboon then cares for the female until she
reaches puberty, only to become the first member of his harem.
Not much different than the worm in the preceding paragraph!
Eisenberg follows the course of his own adoptive experience and
in closing quotes one popular author as essentially bemoaning
the “waste of love” in raising unrelated children. This was in
reference primarily to the children of divorce and remarriage.
But Eisenberg closes with “I can”t speak for stepparents, but the
kind of adoption I know about seems not a waste but a magic
barrel of love, never exhausted, never perhaps explained.”
Allen F. Bortrum
