So why are these compact, high-redshift
galaxies such a theoretical conundrum? Ellip-
tical galaxies have long been seen as the end-
point of galaxy formation: when a star-forming
spiral or irregularly-shaped galaxy, full
of young blue stars, has its star formation
quenched by some astrophysical-feedback
process, it quickly ages to become a ‘red and
dead’ elliptical. As the overall star-formation
rate of the Universe winds down with time, it
seems natural to find an increasing number of
these galaxy fossils full of old red stars. But such
red galaxies are found to be more massive than
any star-forming galaxy, so something extra is
needed to provide the mass.
The consensus has been that elliptical gal-
axies have also assembled through mergers of
smaller galaxies, a process naturally expected
in current galaxy-formation theories
8
. The
most massive ellipticals would be the result
of major mergers of smaller ellipticals — with
these progenitors having been of roughly equal
mass. Elliptical galaxies are observed to follow
tight scaling relationships between size, mass
and velocity, which one might think would
be seriously disturbed by mergers. However,
computer simulations show that mergers sim-
ply ‘move’ the galaxies along the relationships
without making them significantly less tight
9
.
But this picture breaks down when size
evolution is taken into account: if you merge
enough elliptical galaxies at high redshift to
account for the size change, you also make
many more high-mass galaxies than are
observed in the nearby Universe. An alterna-
tive is that if mergers are predominantly minor
— those in which a low-mass object merges
into one of much larger mass — size growth
can be achieved without a substantial increase
in mass
10
. However, low-mass galaxies gener-
ally contain a lot of young stars, so this seems
inconsistent with the observed old stellar pop-
ulations of the high-redshift compact galaxies
and their nearby descendants.
This ‘lack of fit’ with the standard picture of
elliptical-galaxy formation has driven a search
for ways other than mergers by which the size
of these galaxies could have blown up. For
example, feedback processes such as an energy
injection from a supernova
11
or quasar
12
could
achieve that by expelling gas from the galaxy
slowly (or rapidly), making the galaxy’s gravi-
tational potential well shallower and moving
stars into larger orbits. But these processes
require a level of star or quasar activity that has
not been observed. A more exotic explanation
could involve the yet unknown nature of dark
matter.
Any successful explanation of the size evolu-
tion must solve what I call the synchronization
problem, which in my view is the most fun-
damental. The size–mass scaling relationship
is tight in the nearby Universe, and possibly
also at high redshift. It is just the normaliza-
tion of this relationship that evolves. There are
no massive compact elliptical galaxies today.
Therefore, the high-redshift (early-epoch)
compact galaxies must be growing in size with
time (Fig. 1). But, at the same time, the Uni-
verse is making new elliptical galaxies, and
somehow both the growing and the newly
formed galaxies fall within the same tight size–
mass relationship at all epochs. Their evolution
is ‘synchronized’ through some process that is
either a coincidence or an important new piece
of astrophysics.
A lot hinges on the interpretation of van
Dokkum and colleagues’ single velocity-dis-
persion measurement
4
of 1255–0. As large
telescopes acquire new multi-object, near-
infrared spectrographs, we can expect to see
many hundreds of such velocity-dispersion
measurements in the next few years. We can
also expect to see improved measurements of
the structural and environmental properties of
these compact galaxies, which will help us to
figure out how bad the problems we have in
explaining these objects really are. It remains
to be seen whether we need conventional or
novel explanations for their astounding growth
into the most massive elliptical galaxies we
see today. 
Karl Glazebrook is at the Centre for Astrophysics
and Supercomputing, Swinburne University of
Technology, Hawthorn, Victoria 3122, Australia.
e-mail: karl@astro.swin.edu.au
1. Abraham, R. G. et al. Astrophys. J. 669, 184–201 (2007).
2. Cimatti, A. et al. Nature 430, 184–187 (2004).
3. van Dokkum, P. G. et al. Astrophys. J. 638, L59–L62
(2006).
4. van Dokkum, P. G., Kriek, M. & Franx, M. Nature 460,
717–719 (2009).
5. Trujillo, I. et al. Astrophys. J. 692, L118–L122 (2009).
6. Kriek, M. et al. Astrophys. J. 700, 221–231 (2009).
7. Cenarro, A. J. & Trujillo, I. Astrophys. J. 696, L43–L47
(2009).
8. De Lucia, G., Springel, V., White, S. D. M., Croton, D. &
Kauffmann, G. Mon. Not. R. Astron. Soc. 366, 499–509
(2006).
9. Boylan-Kolchin, M., Ma, C.-P. & Quataert, E. Mon. Not. R.
Astron. Soc. 369, 1081–1089 (2006).
10. Bezanson, R. et al. Astrophys. J. 697, 1290–1298 (2009).
11. Damjanov, I. et al. Astrophys. J. 695, 101–115 (2009).
12. Fan, L., Lapi, A., De Zotti, G. & Danese, L. Astrophys. J. 689,
L101–L104 (2008).
ARCHAEOLOGY
The earliest musical tradition
Daniel S. Adler
Music is a ubiquitous element in our daily lives, and was probably just as
important to our early ancestors. Fragments of ancient flutes reveal that
music was well established in Europe by about 40,000 years ago.
The Palaeolithic caves of the Swabian Jura in
southwestern Germany have been a source of
valuable and often provocative archaeological
discoveries for many decades. In particular,
finds of figurative art from the early Aurignacian
— the earliest Upper Palaeolithic archaeologi-
cal culture associated with modern humans in
Europe — suggest that these hunter–gatherers
had the knowledge, expertise, incentive and
time to craft sophisticated objects for use in
ritual activities. These activities probably
served to affirm group affiliation, signal social
identity and mark important social events or
rites of passage. Conard et al.
1
(page 737 of this
issue) now reveal that the Aurignacian inhab-
itants of the Swabian Jura had also mastered
the art of music. Their detailed report high-
lights the discovery of a largely complete flute
(Fig. 1) and two small flute fragments in the
oldest Aurignacian layer at Hohle Fels Cave.
Conard recently reported
2
the discovery of a
female figurine carved from mammoth ivory
in an Aurignacian layer at Hohle Fels dated to
at least 35,000 years ago (based on the newly
calibrated radiocarbon timescale). At present,
this is the earliest such find in the world.
Additional examples of figurative art — of
mammoths, horses, bison, cave lions, waterfowl
and half-human, half-animal ‘therianthropes’
— have also been found in Aurignacian layers
at Hohle Fels and other sites in the Swabian
Jura. These finds suggest that the region was
inhabited by a population of Homo sapiens
sapiens that had mastered, among other
things, the manipulation of mammoth ivory
into three-dimensional, naturalistic forms for
purposes not directly related to daily economic
needs. Just as we continue to do today, these
Figure 1 | Sounds old. Conard et al.
1
have discovered the oldest known flute, at Hohle Fels Cave in
Germany. The flute is made from bird bone, and dates from the early Aurignacian, 40,000 years ago.
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NATURE|Vol 460|6 August 2009 NEWS & VIEWS
693-699 News and Views NS.indd 695 31/7/09 17:49:18
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