HUMAN EVOLUTION
1.
(a)
original concentration of the radioisotope must be established/estimated;
rate of decay/half-life of the isotope must be known;
in radiocarbon dating concentration of the surviving 14C in the fossil
is measured;
in potassium-argon dating ratio of 40K to 40Ar atoms are measured;
(b)
10000 years
(c)
increased bipedalism;
increased brain size/cranial capacity;
reduction of sagittal crest;
tooth size reduction;
flattening of the facial bones;
development of opposable thumb;
2 max
1
2 max
[5]
2.
few hominid fossils have been found/not often found/are very rare;
most hominids/organisms not preserved/decompose;
only teeth and bones remain / soft tissues do not fossilize;
require certain conditions for preservation/dry/anaerobic/quickly covered/frozen;
earlier cultures did not bury the dead / remains were scavenged/dispersed;
acids break down/dissolve teeth/bones;
many missing links/fossils of intermediate stages;
difficult to get conclusive evidence / difficult to falsify theories;
theories change radically with one/few discoveries;
6 max
[6]
3.
(a)
most carbon is 12C but there is small amount of (radioactive) 14C;
organisms absorb the same ratio of 12C:14C as in the environment;
after death, no more atoms accumulate;
14
C steadily breaks down so amount decreases/12C:14C increases with
age / half-life (approx 5730 years) expresses rate of decay of 14C;
the less 14C in a sample the older the fossil / 14C useful for dating samples
one thousand to one hundred thousand years old;
HUMAN EVOLUTION
2 max
1
HUMAN EVOLUTION
(b)
Ardipithecus is an older genus (5.2–4.4 million years ago) than
Australopithecus (4–2.5 million years ago);
toe structure of Ardipithecus shows it was probably bipedal / early
Australopithecus at least partially bipedal;
tooth structure changed as diet changed from soft fruits/leaves/seeds/
nuts to omnivorous diet;
large/primitive canines seen in Ardipithecus to smaller canines
in Australopithecus;
increasing height —Ardipithecus is smaller (the size of a chimpanzee);
change in face from projecting to flat face / from tall to small lower
jaw / development of high forehead / loss of brow ridges;
3 max
[5]
4.
(a)
(b)
Australopithecus afarensis/A. afarensis had a relatively small skull
with a low forehead/moderate sized brow ridges;
A. africanus/A. robustus evolved from A. afarensis with increases
in cranial capacity/larger brow ridges/low forehead;
Homo habilis/H. habilis had a small cranial capacity/small brow
ridges/increased forehead;
H. erectus/H. neanderthalensis/H. sapiens followed H. habilis
and show increased cranial capacity;
(as the Homo sp evolved) the forehead increased;
(as the Homo sp evolved) the orbital ridges decreased;
3 max
improved diet quality correlated (positively) with hominid skull
development/size;
improved diet quality provides energy to support a greater
brain function;
change of habitat (in Africa) 2.5 mya may have prompted
emergence of Homo sp;
change in diet to include meat increased brain size (of hominids);
cooking food enabled hominids to eat a wider variety of food;
2 max
[5]
HUMAN EVOLUTION
2
HUMAN EVOLUTION
5.
cultural evolution based on skills / information passed from one
generation to another;
new methods can be transmitted between different groups;
cultural evolution is learned/taught/language dependent;
large brains of Homo species allow more learning;
cultural evolution allows more rapid evolution / most recent changes are
cultural;
genetic evolution is dependent on/controlled by genes;
genetic evolution is limited by the genetic composition/genotypes of the
populations;
e.g. of human genetic evolution (such as increase in cranial capacity);
e.g. of human cultural evolution (such as tool making/religion/art);
6 max
[6]
6.
(a)
(b)
time taken for the radioactivity/% parental isotope to fall to half of its original
level/for half of the atoms in a given mass to decay;
after 28 years there is 50% of previous reading of strontium-90 isotopes;
2
4 to 2.5 million years ago;
in East Africa;
most complete skeleton Lucy;
Lucy dated to 3.2/3.6 million years ago; (accept any date within this range)
other part-fossils found;
2 max
[4]
7.
fossils being formed is a rare event;
(e.g. fewNeanderthals survived the
example to illustrate why forming fossils is a rare event; 
cold, so few fossils)
fossils being preserved is a rare event;
fossils being found is a rare event; (e.g. due to geographical locations)
chances of finding fossils is improved by searching in the right geological
strata / OWTTE;
poor data / fragmented remains / very small sample size;
more prone to paradigm shifts/changes in theory when data is limited /
discovery of a small amount of fossils can lead to a huge change in theories;
paleoanthropology can still be considered a science e.g. Dmanisi, Georgia
(falsification of earlier positions held);
6 max
[6]
HUMAN EVOLUTION
3
HUMAN EVOLUTION
8.
(a)
(b)
forward facing eyes/binocular vision;
large brains;
flexible shoulder joints / shoulder blades on the dorsal side of the thorax;
manual dexterity / power grip / opposable thumb / grasping limbs;
finger pads / nails not claws;
skull adapted for upright posture;
pronation / rotating hand;
2 max
fossilization is an exceptionally rare occurrence;
most components of formerly living things tend to decompose relatively
quickly following death;
fossilization tends to favour hard body parts;
fossilization favours species that were widespread/lived for a long time;
paleoanthropology is an inductive/data-poor science (a relatively small
amount of data is used to draw conclusions);
many of the conclusions that have been drawn on limited data
have not stood for long;
exposed fossils are soon destroyed/weathered, reducing the chance
of them being found;
new discoveries regularly come to light, leading scientists to
re-interpret previous assumptions in the light of the new data;
examples e.g. the Dmansi site, Georgia, discoveries have led to a
re-evaluation of previous theories of human evolution;
3 max
[5]
9.
(a)
all the genes in an (interbreeding) population
(b)
both involve the formation of new species;
by the isolation of its genetic pool (in both cases);
both provide conditions for natural selection;
sympatric in same geographical area, allopatric in different;
sympatric could be reproductive/behavioural isolation while allopatric
physical isolation;
example of each; (e.g. allopatric speciation of Galapagos finches and
sympatric speciation due to polyploidy)
Award mark only where comparison is clear.
4 max
growth in brain requires more protein;
increased brain correlates with change of diet from plants/leaves to
fruit/meat (higher quality diet);
eating meat provides more protein;
larger brain implies more evolution as learning capacities increase;
2 max
(c)
1
[7]
HUMAN EVOLUTION
4
HUMAN EVOLUTION
10.
(a)
(b)
cultural evolution involves passing of technology/language/customs
from one generation to the next / does not affect the gene pool/change
the genetic makeup while genetic evolution involves passing of
genes/genetic mutations from one generation to another / OWTTE;
cultural evolution allows for faster changes than genetic evolution;
Accept any other valid difference.
1 max
long stable periods / little change;
short periods of sudden/rapid evolution;
e.g. volcanic evolution/meteor impact causing sudden climatic/
environmental changes / other valid examples;
2 max
[3]
11.
(a)
(b)
(c)
(d)
both involve reproductive isolation / separation of gene pools;
sympatric is speciation due to isolation of populations living in the same
geographic area whereas allopatric is speciation due to geographic isolation;
2
analogous structure similar in appearance/function but with different
evolutionary history e.g. wing of bat and wing of bird;
1
smaller/70S ribosomes in mitochondria/chloroplasts (as in prokaryotes);
circular DNA in mitochondria/chloroplasts (as in prokaryotes);
mitochondria/chloroplasts have double membrane;
similar size/shape of mitochondria/chloroplasts to prokaryotes;
2 max
opposable thumb;
large range of shoulder movement;
good vision / stereoscopic vision / overlapping field view;
large brain relative to body size;
tailless primate;
Y-5 cusps of molars;
2 max
[7]
12.
(a)
time for radiation material to decay to half its original amount / activity / mass
HUMAN EVOLUTION
1
5
HUMAN EVOLUTION
(b)
gradualism: slow, continuous change over a long period of time;
gradual accumulation of (neutral) mutations / variations;
punctuated equilibrium: long periods of stability followed by sudden changes;
fossil record supports this;
natural selection can be intense and can cause rapid change / evolution;
rapid evolution due to major environmental changes / volcanic eruptions /
meteor impact / other example;
only advantageous alleles ultimately survive;
some mutations had no morphological effects so not visible in the fossil record;
rate of evolution could have fluctuated over time;
6 max
Award [4 max] if only one idea is discussed.
[7]
13.
(a)
tool making first associated with H. habilis;
requires larger brain;
brain requires vast amounts of energy / consumes 40% of energy intake;
so larger brain size had an effect on diet requirements / created a demand for
changes in diet;
food scarcity may lead to decrease in brain size;
change to higher calorific diet may allow increase in brain size;
more complex tool making / human society / language development required
larger brain size;
larger brain / better cognitive skills allowed for better hunting and gathering;
led to greater calorific intake;
about 2.5 MYBP (million years before present) animal foods began to
occupy an increasingly prominent place in diet;
animal tissues can provide the necessary structural lipid for human brain
expansion;
changes in the dental fossil record are indirect evidence for such a change
in diet;
[5]
HUMAN EVOLUTION
6