Sir
Francis Galton, FRS ( 1822 – 1911), was an English Victorian era
polymath: a statistician, sociologist, psychologist, anthropologist,
eugenicist, tropical explorer, geographer, inventor, meteorologist,
proto-geneticist, and psychometrician. He was knighted in 1909.
Galton
produced over 340 papers and books. He also created the statistical
concept of correlation and widely promoted regression toward the mean.
He was the first to apply statistical methods to the study of human
differences and inheritance of intelligence, and introduced the use of
questionnaires and surveys for collecting data on human communities,
which he needed for genealogical and biographical works and for his
anthropometric studies. He was a pioneer of eugenics, coining the term
itself in 1883, and also coined the phrase "nature versus nurture". His
book Hereditary Genius (1869) was the first social scientific attempt to
study genius and greatness.
As
an investigator of the human mind, he founded psychometrics (the
science of measuring mental faculties) and differential psychology, as
well as the lexical hypothesis of personality. He devised a method for
classifying fingerprints that proved useful in forensic science. He also
conducted research on the power of prayer, concluding it had none due
to its null effects on the longevity of those prayed for. His quest for
the scientific principles of diverse phenomena extended even to the
optimal method for making tea.
As
the initiator of scientific meteorology, he devised the first weather
map, proposed a theory of anticyclones, and was the first to establish a
complete record of short-term climatic phenomena on a European scale.
He also invented the Galton Whistle for testing differential hearing
ability. He was Charles Darwin's half-cousin.
The exceedingly
close resemblance attributed to twins has been the subject of many
novels and plays, and most persons have felt a desire to know upon what
basis of truth those works of fiction may rest. But twins have many
other claims to attention, one of which will be discussed in the present
memoir. It is, that their history affords means of distinguishing
between the effects of tendencies received at birth, and of those that
were imposed by the circumstances of their after lives; in other words,
between the effects of nature and of nurture. This is a subject of
especial importance in its bearings on investigations into mental
heredity, and I, for my part, have keenly felt the difficulty of drawing
the necessary distinction whenever I tried to estimate the degree in
which mental ability was, on the average, inherited. The objection to
statistical evidence in proof of its inheritance has always been: “The
persons whom you compare may have lived under similar social conditions
and have had similar advantages of education, but such prominent
conditions are only a small part of those that determine the future of
each man's life. It is to trifling accidental circumstances that the
bent of his disposition and his success are mainly due, and these you
leave wholly out of account, in fact, they do not admit of being
tabulated, and therefore your statistics, however plausible at first
sight, are really of very little use.” No method of enquiry which I have
been able to carry out, and I have tried many methods, is wholly free
from this objection. I have therefore attacked the problem from the
opposite side, seeking for some new method by which it would be possible
to weigh in just scales the respective effects of nature and nurture,
and to ascertain their several shares in framing the disposition and
intellectual ability of men. The life history of twins supplies what I
wanted. We might begin by enquiring about twins who were closely alike
in boyhood and youth, and who were educated together for many years, and
learn whether they subsequently grew unlike, and, if so, what the main
causes were which, in the opinion of the family, produced the
dissimilarity. In this way we may obtain much direct evidence of the
kind we want; but we can also obtain yet more valuable evidence by a
converse method. We can enquire into the history of twins who were
exceedingly unlike in childhood, and learn how far they became
assimilated under the influence of their identical nurtures; having the
same home, the same teachers, the same associates, and in every other
respect the same surroundings.
My materials were
obtained by sending circulars of enquiry to persons who were either
twins themselves or the near relations of twins. The printed questions
were in thirteen groups; the last of them asked for the addresses of
other twins known to the recipient who might be likely to respond if I
wrote to them. This happily led to a continually widening circle of
correspondence, which I pursued until enough material was accumulated
for a general reconnaissance of the subject.
The reader will
easily understand that the word “twins” is a vague expression, which
covers two very dissimilar events; the one corresponding to the progeny
of animals that have usually more than one young one at a birth, and the
other corresponding to those double-yolked eggs that are due to two
germinal spots in a single ovum. The consequence of this is, that I find
a curious discontinuity in my results. One would have expected that
twins would commonly be found to possess a certain average likeness to
one another; that a few would greatly exceed that degree of likeness,
and a few would greatly fall short of it; but this is not at all the
case. Twins may be divided into three groups, so distinct that there are
not many intermediate instances; namely, strongly alike, moderately
alike, and extremely dissimilar. When the twins are a boy and a girl,
they are never closely alike; in fact, their origin never corresponds to
that of the above-mentioned double-yolked eggs.
I have received
about eighty returns of cases of close similarity, thirty-five of which
entered into many instructive details. In a few of these not a single
point of difference could be specified. In the remainder, the colour of
the hair and eyes were almost always identical; the height, weight, and
strength were generally very nearly so, but I have a few cases of a
notable difference in these, notwithstanding the resemblance was
otherwise very near. The manner and address of the thirty-five pairs of
twins is usually described as being very similar, though there often
exists a difference of expression familiar to near relatives but
unperceived by strangers. The intonation of the voice when speaking is
commonly the same, but it frequently happens that the twins sing in
different keys. Most singularly, that one point in which similarity is
rare is the handwriting. I cannot account for this, considering how
strongly handwriting runs in families, but I am sure of the fact. I have
only one case in which nobody, not even the twins themselves, could
distinguish their own notes of lectures, etc.; barely two or three in
which the handwriting was undistinguishable by others, and only a few in
which it was described as closely alike. On the other hand, I have many
in which it is stated to be unlike, and some in which it is alluded to
as the only point of difference.
One of my enquiries
was for anecdotes as regards the mistakes made by near relatives between
the twins. They are numerous, but not very varied in character. When
the twins are children, they have commonly to be distinguished by
ribbons tied round their wrist or neck; nevertheless the one is
sometimes fed, physicked, and whipped by mistake for the other, and the
description of these little domestic catastrophes is usually given to me
by the mother, in a phraseology that is somewhat touching by reason of
its seriousness. I have one case in which a doubt remains whether the
children were not changed in their bath, and the presumed A is not
really B, and vice versa. In another case an artist was engaged on the
portraits of twins who were between three and four years of age; he had
to lay aside his work for three weeks, and, on resuming it, could not
tell to which child the respective likenesses he had in hand belonged.
The mistakes are less numerous on the part of the mother during the
boyhood and girlhood of the twins, but almost as frequent on the part of
strangers. I have many instances of tutors being unable to distinguish
their twin pupils. Thus, two girls used regularly to impose on their
music teacher when one of them wanted a whole holiday; they had their
lessons at separate hours, and the one girl sacrificed herself to
receive two lessons on the same day, while the other one enjoyed
herself. Here is a brief and comprehensive account: “Exactly alike in
all, their schoolmasters never could tell them apart; at dancing parties
they constantly changed partners without discovery; their close
resemblance is scarcely diminished by age.” The following is a typical
schoolboy anecdote: Two twins were fond of playing tricks, and
complaints were frequently made; but the boys would never own which was
the guilty one, and the complainants were never certain which of the two
he was. One head master used to say he would never flog the innocent
for the guilty, and another used to flog both. No less than nine
anecdotes have reached me of a twin seeing his or her reflection in a
looking-glass, and addressing it, in the belief it was the other twin in
person. I have many anecdotes of mistakes when the twins were nearly
grown up. Thus: “Amusing scenes occurred at college when one twin came
to visit the other; the porter on one occasion refused to let the
visitor out of the college gates, for, though they stood side by side,
he professed ignorance as to which he ought to allow to depart.”
Children are usually
quick in distinguishing between their parents and his or her twin: but I
have two cases to the contrary. Thus, the daughter of a twin says:
“Such was the marvellous similarity of their features, voice, manner,
etc. that I remember, as a child, being very much puzzled, and I think,
had my aunt lived much with us, I should have ended by thinking I had
two mothers.” The other, a father of twins, remarks: “We were extremely
alike, and are so at this moment, so much so that our children up to
five and six years old did not know us apart.”
I have four or five
instances of doubt during an engagement of marriage. Thus: “A married
first, but both twins met the lady together for the first time, and fell
in love with her there and then. A managed to see her home and to gain
her affection, though B went sometimes courting in his place, and
neither the lady nor her parents could tell which was which.” I have
also a German letter, written in quaint terms, about twin brothers who
married sisters, but could not easily be distinguished by them. In the
well-known novel by Mr. Wilkie Collins of “Poor Miss Finch,” the blind
girl distinguishes the twin she loves by the touch of his hand, which
gives her a thrill that the touch of the other brother does not.
Philosophers have not, I believe, as yet investigated the conditions of
such thrills; but I have a case in which Miss Finch's test would have
failed. Two persons, both friends of a certain twin lady, told me that
she had frequently remarked to them that “kissing her twin sister was
not like kissing her other sisters, but like kissing herself, her own
hand, for example.”
It would be an
interesting experiment for twins who were closely alike, to try how far
dogs could distinguish between them by scent.
I have a few
anecdotes of strange mistakes made between twins in adult life. Thus, an
officer writes: “On one occasion when I returned from foreign service
my father turned to me and said, 'I thought you were in London,'
thinking I was my brother, yet he had not seen me for nearly four years,
our resemblance was so great.”
The next and last
anecdote I shall give is, perhaps, the most remarkable of those that I
have: it was sent me by the brother of the twins, who were in middle
life at the time of its occurrence: “A was again coming home from India,
on leave; the ship did not arrive for some days after it was due; the
twin brother B had come up from his quarters to receive A, and their old
mother was very nervous. One morning A rushed in, saying, 'Oh, mother,
how are you?' Her answer was, 'No, B, it's a bad joke; you know how
anxious I am!' and it was a little time before A could persuade her that
he was the real man.”
Enough has been said
to prove that an extremely close personal resemblance frequently exists
between twins of the same sex; and that, although the resemblance
usually diminishes as they grow into manhood and womanhood, some cases
occur in which the resemblance is lessened in a hardly perceptible
degree. It must be borne in mind that the divergence of development,
when it occurs, need not be ascribed to the effect of different
nurtures, but that it is quite possible that it may be due to the
appearance of qualities inherited at birth, though dormant, like gout,
in early life. To this I shall recur.
There is a curious
feature in the character of the resemblance between twins, which has
been alluded to by a few correspondents: it is well illustrated by the
following quotations. A mother of twins says: “There seems to be a sort
of interchangeable likeness in expression, that often gave to each the
affect of being more like his brother than himself.” Again, two twin
brothers, writing to me, after analysing their points of resemblance,
which are close and numerous, and pointing out certain shades of
difference, add: “These seem to have marked us through life, though for a
while when we were first separated, the one to go to business, and the
other to college, our respective characters were inverted; we both think
that at that time we each ran into the character of the other. The
proof of this consists in our own recollections, in our correspondence
by letter, and in the views which we then took of matters in which we
were interested.” In explanation of this apparent interchangeableness,
we must recollect that no character is simple, and that in twins who
strongly resemble each other every expression in the one may be matched
by a corresponding expression in the other, but it does not follow that
the same expression should be the dominant one in both cases. Now it is
by their dominant expressions that we should distinguish between the
twins; consequently when one twin has temporarily the expression which
is the dominant one in his brother, he is apt to be mistaken for him.
There are also cases where the development of the two twins is not
strictly by equal steps; they reach the same goal at the same time, but
not by identical stages. Thus: A is born the larger, then B overtakes
and surpasses A, the end being that the twins become closely alike. This
process would aid in giving an interchangeable likeness at certain
periods of their growth, and is undoubtedly due to nature more
frequently than to nurture.
Among my thirty-five
detailed cases of close similarity, there are no less than seven in
which both twins suffered from some special ailment or had some
exceptional peculiarity. One twin writes that she and her sister “have
both the defect of not being able to come down stairs quickly, which,
however, was not born with them, but came on at the age of twenty.”
Another pair of twins have a slight congenital flexure of one of the
joints of the little finger: it was inherited from a grandmother, but
neither parents, nor brothers, nor sisters show the least trace of it.
In another case, one was born ruptured, and the other became so at six
months old. Two twins at the age of twenty-three were attacked by
toothache, and the same tooth had to be extracted in each case. There
are curious and close correspondences mentioned in the falling off of
the hair. Two cases are mentioned of death from the same disease; one of
which is very affecting. The outline of the story was that the twins
were closely alike and singularly attached, and had identical tastes;
they both obtained Government clerkships, and kept house together, when
one sickened and died of Bright's disease, and the other also sickened
of the same disease and died seven months later.
In no less than nine
out of the thirty-five cases does it appear that both twins are apt to
sicken at the same time. This implies so intimate a constitutional
resemblance, that it is proper to give some quotations in evidence.
Thus, the father of two twins says: “Their general health is closely
alike; whenever one of them has an illness the other invariably has the
same within a day or two, and they usually recover in the same order.
Such has been the case with whooping cough, chicken-pox, and measles;
also with slight bilious attacks, which they have successively.
Latterly, they had a feverish attack at the same time.” Another parent
of twins says: “If anything ails one of them, identical symptoms nearly
always appear in the other: this has been singularly visible in two
instances during the last two months. Thus, when in London, one fell ill
with a violent attack of dysentery, and within twenty-four hours the
other had precisely the same symptoms.”
A medical man writes
of twins with whom he is well acquainted: “Whilst I knew them, for a
period of two years, there was not the slightest tendency towards a
difference in body or mind; external influences seemed powerless to
produce any dissimilarity.” The mother of two other twins, after
describing how they were ill simultaneously up to the age of fifteen,
adds, that they shed their first milk teeth within a few hours of each
other.
Trousseau has a very
remarkable case (in the chapter on Asthma) in his important work,
“Clinique Médicale.” It was quoted at length in the original French in
Mr. Darwin's “Variation Under Domestication,” - The following is a
translation:
“I attended twin
brothers so extraordinarily alike, that it was impossible for me to tell
which was which without seeing them side by side. But their physical
likeness extended still deeper for they had, so to speak, a yet more
remarkable pathological resemblance. Thus, one of them, whom I saw at
the Néothermes at Paris, suffering from rheumatic ophthalmia, said to
me, 'At this instant, my brother must be having an ophthalmia like
mine;' and, as I had exclaimed against such an assertion, he showed me a
few days afterwards a letter just received by him from his brother, who
was at that time at Vienna, and who expressed himself in these words:
'I have my ophthalmia; you must be having yours.' However singular this
story may appear, the fact is none the less exact: it has not been told
to me by others, but I have seen it myself; and I have seen other
analogous cases in my practice. These twins were also asthmatic, and
asthmatic to a frightful degree. Though born in Marseilles, they never
were able to stay in that town, where their business affairs required
them to go, without having an attack. Still more strange, it was
sufficient for them to get away only as far as Toulon in order to be
cured of the attack caught at Marseilles. They travelled continually,
and in all countries, on business affairs, and they remarked that
certain localities were extremely hurtful to them, and that in others
they were free from all asthmatic symptoms.”
I do not like to
pass over here a most dramatic tale in the Psychologie Morbide of Dr. J.
Moreau (de Tours), Médecin de l'Hospice de Bicetre. Paris, 1859 - . He
speaks “of two twin brothers who had been confined, on account of
monomania, at Bicetre.... Physically the two young men are so nearly
alike that the one is easily mistaken for the other. Morally, their
resemblance is no less complete, and is most remarkable in its details.
Thus, their dominant ideas are absolutely the same. They both consider
themselves subject to imaginary persecutions; the same enemies have
sworn their destruction, and employ the same means to effect it. Both
have hallucinations of hearing. They are both of them melancholy and
morose; they never address a word to anybody, and will hardly answer the
questions that others address to them. They always keep apart and never
communicate with one another. An extremely curious fact which has been
frequently noted by the superintendents of their section of the
hospital, and by myself, is this: From time to time, at very irregular
intervals of two, three, and many months, without appreciable cause, and
by the purely spontaneous effect of their illness, a very marked change
takes place in the condition of the two brothers. Both of them, at the
same time, and often on the same day, rouse themselves from their
habitual stupor and prostration; they make the same complaints, and they
come of their own accord to the physician, with an urgent request to be
liberated. I have seen this strange thing occur, even when they were
some miles apart, the one being at Bicetre and the other living at
Sainte-Anne.”
Dr. Moreau ranked as
a very considerable medical authority, but I cannot wholly accept this
strange story without fuller information. Dr. Moreau writes it in too
off-hand a way to carry the conviction that he had investigated the
circumstances with the sceptic spirit and scrupulous exactness which so
strange a phenomenon would have required. If full and precise notes of
the case exist, they certainly ought to be published at length. I sent a
copy of this passage to the principal authorities among the physicians
to the insane in England, asking if they had ever witnessed any similar
case. In reply, I have received three noteworthy instances, but none to
be compared in their exact parallelism with that just given. The details
of these three cases are painful, and it is not necessary to my general
purpose that I should further allude to them.
There is another
curious French case of insanity in twins, which was pointed out to me by
Professor Paget, described by Dr. Baume in the Annales
Medico-Psychologiques, - of which the following is an abstract. The
original contains a few more details, but it is too long to quote:
Francois and Martin, fifty years of age, worked as railroad contractors
between Quimper and Châteaulin. Martin had twice had slight attacks of
insanity. On January 15, a box in which the twins deposited their
savings was robbed. On the night of January 23-4 both Francois (who
lodged at Quimper) and Martin (who lived with his wife and children at
St. Lorette, two leagues from Quimper) had the same dream at the same
hour, three A. M., and both awoke with a violent start, calling out, “I
have caught the thief! I have caught the thief! they are doing injury to
my brother!” They were both of them extremely agitated, and gave way to
similar extravagances, dancing and leaping. Martin sprang on his
grandchild, declaring that he was the thief, and would have strangled
him if he had not been prevented: he then became steadily worse,
complained of violent pains in his head, went out of doors on some
excuse, and tried to drown himself in the River Steir, but was forcibly
stopped by his son, who had watched and followed him. He was then taken
to an asylum by gendarmes, where he died in three days. Francois, on his
part calmed down on the morning of the 24th, and employed the day in
enquiring about the robbery. By a strange chance he crossed his
brother's path at the moment when the latter was struggling with the
gendarmes; then he himself became maddened, giving way to extravagant
gestures and making incoherent proposals (similar to those of his
brother). He then asked to be bled, which was done, and afterwards,
declaring himself to be better, went out on the pretext of executing
some commission, but really to drown himself in the River Steir, which
he actually did, at the very spot where Martin had attempted to do the
same thing a few hours previously.
The next point which
I shall mention, in illustration of the extremely close resemblance
between certain twins, is the similarity in the association of their
ideas. No less than eleven out of the thirty-five cases testify to this.
They make the same remarks on the same occasion, begin singing the same
song at the same moment, and so on; or one would commence a sentence,
and the other would finish it. An observant friend graphically described
to me the effect produced on her by two such twins whom she had met
casually. She said: “Their teeth grew alike, they spoke alike and
together, and said the same things, and seemed just like one person.”
One of the most curious anecdotes that I have received concerning this
similarity of ideas was that one twin A, who happened to be at a town in
Scotland, bought a set of champagne glasses which caught his attention,
as a surprise for his brother B; while at the same time, B, being in
England, bought a similar set of precisely the same pattern as a
surprise for A. Other anecdotes of a like kind have reached me about
these twins.
The last point to
which I shall allude regards the tastes and dispositions of the
thirty-five pairs of twins. In sixteen cases - that is, in nearly one
half of them - these were described as closely similar; in the remaining
nineteen they were much alike, but subject to certain named
differences. These differences belonged almost wholly to such groups of
qualities as these: The one was the more vigorous, fearless, energetic;
the other was gentle, clinging, and timid: or, again, the one was more
ardent, the other more calm and gentle; or again, the one was the more
independent, original, and self-contained; the other the more generous,
hasty, and vivacious. In short the difference was always that of
intensity or energy in one or other of its protean forms: it did not
extend more deeply into the structure of the characters. The more
vivacious might be subdued by ill health, until he assumed the character
of the other; or the latter might be raised by excellent health to that
of the former. The difference is in the key-note, not in the melody.
It follows from what
has been said concerning the similar dispositions of the twins, the
similarity in the associations of their ideas, of their special
ailments, and of their illnesses generally, that the resemblances are
not superficial, but extremely intimate. I have only two cases
altogether of a strong bodily resemblance being accompanied by mental
diversity, and one case only of the converse kind. It must be remembered
that the conditions which govern extreme likeness between twins are not
the same as those between ordinary brothers and sisters (I may have
hereafter to write further about this); and that it would be wholly
incorrect to generalize from what has just been said about the twins,
that mental and bodily likeness are invariably co-ordinate; such being
by no means the case.
We are now in a
position to understand that the phrase “close similarity” is no
exaggeration, and to realize the value of the evidence about to be
adduced. Here are thirty-five cases of twins who were “closely alike” in
body and mind when they were young, and who have been reared exactly
alike up to their early manhood and womanhood. Since then the conditions
of their lives have changed; what change of conditions has produced the
most variation?
It was with no
little interest that I searched the records of the thirty-five cases for
an answer; and they gave an answer that was not altogether direct, but
it was very distinct, and not at all what I had expected. They showed me
that in some cases the resemblance of body and mind had continued
unaltered up to old age, notwithstanding very different conditions of
life; and they showed in the other cases that the parents ascribed such
dissimilarity as there was wholly, or almost wholly, to some form of
illness. In four cases it was scarlet fever; in one case, typhus; in
one, a slight effect was ascribed to a nervous fever: then I find
effects from an Indian climate; from an illness (unnamed) of nine
months' duration; from varicose veins; from a bad fracture of the leg,
which prevented all active exercise afterwards; and there were three
other cases of ill health. It will be sufficient to quote one of the
returns; in this the father writes:
“At birth they were
exactly alike, except that one was born with a bad varicose affection,
the effect of which had been to prevent any violent exercise, such as
dancing, or running, and, as she has grown older, to make her more
serious and thoughtful. Had it not been for this infirmity, I think the
two would have been as exactly alike as it is possible for two women to
be, both mentally and physically; even now they are constantly mistaken
for one another.”
In only a very few
cases is there some allusion to the dissimilarity being partly due to
the combined action of many small influences, and in no case is it
largely, much less wholly, ascribed to that cause. In not a single
instance have I met with a word about the growing dissimilarity being
due to the action of the firm, free will of one or both of the twins,
which had triumphed over natural tendencies; and yet a large proportion
of my correspondents happen to be clergymen whose bent of mind is
opposed, as I feel assured from the tone of their letters, to a
necessitarian view of life.
It has been remarked
that a growing diversity between twins may be ascribed to the tardy
development of naturally diverse qualities; but we have a right, upon
the evidence I have received, to go further than this. We have seen that
a few twins retain their close resemblance through life; in other
words, instances do exist of thorough similarity of nature, and in these
external circumstances do not create dissimilarity. Therefore, in those
cases, where there is a growing diversity, and where no external cause
can be assigned either by the twins themselves or by their family for
it, we may feel sure that it must be chiefly or altogether due to a want
of thorough similarity in their nature. Nay further, in some cases it
is distinctly affirmed that the growing dissimilarity can be accounted
for in no other way. We may therefore broadly conclude that the only
circumstance, within the range of those by which persons of similar
conditions of life are affected, capable of producing a marked effect on
the character of adults, is illness or some accident which causes
physical infirmity. The twins who closely resembled each other in
childhood and early youth, and were reared under not very dissimilar
conditions, either grow unlike through the development of natural
characteristics which had lain dormant at first, or else they continue
their lives, keeping time like two watches, hardly to be thrown out of
accord except by some physical jar. Nature is far stronger than nurture
within the limited range that I have been careful to assign to the
latter.
The effect of
illness, as shown by these replies, is great, and well deserves further
consideration. It appears that the constitution of youth is not so
elastic as we are apt to think, but that an attack, say of scarlet
fever, leaves a permanent mark, easily to be measured by the present
method of comparison. This recalls an impression made strongly on my
mind several years ago by the sight of a few curves drawn by a
mathematical friend. He took monthly measurements of the circumference
of his children's heads during the first few years of their lives, and
he laid down the successive measurements on the successive lines of a
piece of ruled paper, by taking the edge of the paper as a base. He then
joined the free ends of the lines, and so obtained a curve of growth.
These curves had, on the whole, that regularity of sweep that might have
been expected, but each of them showed occasional halts, like the
landing places on a long flight of stairs. The development had been
arrested by something, and was not made up for by after growth. Now, on
the same piece of paper my friend had also registered the various
infantile illnesses of the children, and corresponding to each illness
was one of these halts. There remained no doubt in my mind that, if
these illnesses had been warped off, the development of the children
would have been increased by almost the precise amount lost in these
halts. In other words, the disease had drawn largely upon the capital,
and not only on the income, of their constitutions. I hope these remarks
may induce some men of science to repeat similar experiments on their
children of the future. They may compress two years of a child's history
on one side of a ruled half-sheet of foolscap paper if they cause each
successive line to stand for a successive month, beginning from the
birth of the child; and if they mark off the measurements by laying, not
the 0-inch division of the tape against the edge of the pages, but,
say, the 10-inch division - in order to economize space.
The steady and
pitiless march of the hidden weaknesses in our constitutions, through
illness to death, is painfully revealed by these histories of twins. We
are too apt to look upon illness and death as capricious events, and
there are some who ascribe them to the direct effect of supernatural
interference, whereas the fact of the maladies of two twins being
continually alike, shows that illness and death are necessary incidents
in a regular sequence of constitutional changes, beginning at birth,
upon which external circumstances have, on the whole, very small effect.
In cases where the maladies of the twins are continually alike, the
clock of life moves regularly on, governed by internal mechanism. When
the hand approaches the hour mark, there is a sudden click, followed by a
whirling of wheels; at the culminating moment, the stroke falls.
Necessitarians may derive new arguments from the life histories of
twins.
We will now consider
the converse side of our subject. Hitherto we have investigated cases
where the similarity at first was close, but afterwards became less: now
we will examine those in which there was great dissimilarity at first,
and will see how far an identity of nurture in childhood and youth
tended to assimilate them. As has been already mentioned, there is a
large proportion of cases of sharply contrasted characteristics, both of
body and mind, among twins. I have twenty such cases, given with much
detail. It is a fact, that extreme dissimilarity, such as existed
between Esau and Jacob, is a no less marked peculiarity in twins of the
same sex, than extreme similarity. On this curious point, and on much
else in the history of twins, I have many remarks to make, but this is
not the place to make them.
The evidence given
by the twenty cases above mentioned is absolutely accordant, so that the
character of the whole may be exactly conveyed by two or three
quotations. One parent says: “They have had exactly the same nurture
from their birth up to the present time; they are both perfectly healthy
and strong, yet they are otherwise as dissimilar as two boys could be,
physically, mentally, and in their emotional nature. ” Here is another
case: “I can answer most decidedly that the twins have been perfectly
dissimilar in character, habits, and likeness from the moment of their
birth to the present time, though they were nursed by the same woman,
went to school together, and were never separated till the age of
fifteen.” Here again is one more, in which the father remarks: “They
were curiously different in body and mind from their birth.” The
surviving twin (a senior wrangler of Cambridge) adds: “A fact struck all
our school contemporaries, that my brother and I were complementary, so
to speak, in point of ability and disposition. He was contemplative,
poetical, and literary to a remarkable degree, showing great power in
that line. I was practical, mathematical, and linguistic. Between us we
should have made a very decent sort of a man.” I could quote others just
as strong as these, while I have not a single case in which my
correspondents speak of originally dissimilar characters having become
assimilated through identity of nurture. The impression that all this
evidence leaves on the mind is one of some wonder whether nurture can do
anything at all beyond giving instruction and professional training. It
emphatically corroborates and goes far beyond the conclusions to which
we had already been driven by the cases of similarity. In these, the
causes of divergence began to act about the period of adult life, when
the characters had become somewhat fixed; but here the causes conducive
to assimilation began to act from the earliest moment of the existence
of the twins, when the disposition was most pliant, and they were
continuous until the period of adult life. There is no escape from the
conclusion that nature prevails enormously over nurture when the
differences of nurture do not exceed what is commonly to be found among
persons of the same rank of society and in the same country. My only
fear is that my evidence seems to prove too much and may be discredited
on that account, as it seems contrary to all experience that nurture
should go for little. But experience is often fallacious in ascribing
great effects to trifling circumstances. Many a person has amused
himself with throwing bits of stick into a tiny brook and watching their
progress; how they are arrested, first by one chance obstacle, then by
another; and again, how their onward course is facilitated by a
combination of circumstances. He might ascribe much importance to each
of these events, and think how largely the destiny of the stick has been
governed by a series of trifling accidents. Nevertheless all the sticks
succeed in passing down the current, and they travel, in the long run,
at nearly the same rate. So it is with life in respect to the several
accidents which seem to have had a great effect upon our careers. The
one element, which varies in different individuals, but is constant in
each of them, is the natural tendency; it corresponds to the current in
the stream, and invariably asserts itself. More might be added on this
matter, and much might be said in qualification of the broad conclusions
to which we have arrived, as to the points in which education appears
to create the most permanent effect; how far by training the intellect
and how far by subjecting the boy to a higher or lower tone of public
opinion; but this is foreign to my immediate object. The latter has been
to show broadly, and, I trust, convincingly, that statistical
estimation of natural gifts by a comparison of successes in life, is not
open to the objection stated at the beginning of this memoir. We have
only to take reasonable care in selecting our statistics, and then we
may safely ignore the many small differences in nurture which are sure
to have characterized each individual case.
