The Calpe Conference 2024: A personal view Part Three

By Dr Alex Menez

The final part of the series in which Dr Alex Menez looks into the Calpe Conference which took place earlier this year and shares his view of the discussions.

The final day began with a talk by Professor Juan Manuel Jiménez-Arenas from the University of Granada.
The Guadix-Baza Basin is located in Granada. The basin, Juan explained, is surrounded by some of the highest mountain ranges on Iberia, “giving it a certain degree of isolation,” and is “one of the richest Pleistocene vertebrate fossil records in Western Eurasia.”
The Orce Basin Archaeological Zone, situated at the north-east of the Guadix-Baza Basin, is of great interest and he added that it “provides evidence of two of the earliest sites with Homo presence in Western Eurasia;” with Barranco León at 1.4 Ma (millions of years ago), and Fuente Nueva 3 at 1.2 Ma.

Research in assessing the palaeoecological context of hominin settlements indicated that “during the Early Pleistocene, the climate and habitat of Orce were Mediterranean,” these being similar to the present but more humid.
There was the possibility, he noted, that Orce may have acted as an “interior island,” this “serving as an ecological refugium where numerous taxa, including Homo, found suitable conditions to develop their lives under the sun of the southern Iberian Peninsula.”

Next on was Professor Juan Arroyo from the University of Seville who described the biogeographical importance of the Strait of Gibraltar for plant ecology and evolution.
He noted that on Earth there is uneven distribution of “biodiversity, the diversity of life across all levels from genes to ecosystems” as a result of “geomorphological and historical dynamics and their interplay with organisms.”

The concept of biodiversity hotspots, which ecologists in the audience would undoubtedly be familiar with, are “regions and sites of high biological diversity.”
Juan explained that one, located in the Mediterranean Basin, “is subdivided in sub-hotspots coinciding mostly with mountains, islands, and refuges,” adding that “one of such Mediterranean Basin ten sub-hotspots is the Baetic-Rifan complex, which is divided by the Strait of Gibraltar.”

He noted that the region is “different from surrounding areas… in some respects, time is frozen and pre-Mediterranean relics are frequent.”
Relict species are of great interest to ecologists and “are relevant at the levels of phylogenetic, phylogeographic, and population ecology.”
He held that, at a wider scale, “this two-side island might be considered as a continental part of the evolutionary archipelago of Macaronesia.”

Scientists constantly look for evidence in their work. On occasion, however, an element of absorption relating to an idea may engender a mental assessment of the implications of a hypothesis. This approach is called a thought experiment and is always rewarding.

Professors Geraldine and Clive Finlayson, and Dr Stewart Finlayson, all from the Gibraltar National Museum, University of Gibraltar, and Liverpool John Moores University; and I from the Gibraltar National Museum and University of Gibraltar, contemplated “what if Neanderthals had reached the Atlantic Islands?”
Geraldine described the diverse research relating to Neanderthals undertaken over decades in Gibraltar, including ecology and behaviour. This, and the characteristics of the Macaronesian islands, set the scene for the thought experiment.

She noted that “suitable conditions” had been found for Neanderthals in the Macaronesian islands. Although large terrestrial mammals were not available, “they would exploit other resources, including sea bird colonies…and would have access to seals, dolphin, and fish.”

Would the Neanderthals, “with different resources… have experienced significant body size reductions as a response to limited sources?”
Homo floresiensis, also known as Flores Man or Hobbit, is the smallest known species of Homo and inhabited the island of Flores, Indonesia, until the arrival of modern humans about 50,000 years ago.

To finish, she said that “we could ask ourselves: had the Neanderthals reached the Macaronesian islands… would we have found evidence of their remains, and would we be talking of a Macaronesian Neanderthal Hobbit here today?”

Following lunch, the next presentation was by Professor Geoff Bailey from the University of York who explained the context of his lecture as “the increasingly well documented and well resolved pattern of sea-level change during human history.”

He explained that today “we are increasingly concerned about the humanly induced causes and social impact of global warming.”
There is the prospect, he noted, of “one metre or more in the coming 100 years,” adding that “it is a sobering commentary on present fears for the future that past human populations have repeatedly faced similar changes.”

These, he described, were similar in “terms of their pace of change, but vastly different in their magnitude.”
The most recent glacial-interglacial climate cycle was around 100,000 years ago and, Geoff noted, “sea-level dropped to 130 metres below the present,” this level remaining for about 10,000 years “before rising to the present level and progressively drowning some 20 million square kilometres of previously exposed land.”

Geoff, an archaeologist who has worked for decades at terrestrial, coastal, and submerged sites, described the consequences of the loss of land “for recognizing the differential visibility or destruction of archaeological evidence in coastal regions; for reconstructing the changing palaeogeography of coastlines, archipelagoes and offshore islands.”

These and other consequences, including investigating “the ecological and social impact of sea-level fall and sea-level rise on past patterns of human settlement and dispersal,” have, he said, “been repeatedly discounted in archaeological and anthropological discourse.”

The next presentation was by Professors Christoph Zollikofer and Marcia S. Ponce de León, both from the University of Zurich.
Neanderthal extinction and possible reasons for this have kept paleoanthropologists busy for decades. Christoph and Marcia provided information from their research including computational modelling approaches to address this and related issues, and noted that “among the many factors that could have contributed to their extinction, two are of particular interest: intra-/inter-specific population dynamics and local/global climate dynamics.”

They contextualized these as hypotheses which also applied to Denisovans. Were “Neanderthals too specialized? No longer adapted to changing environmental conditions? Genetically assimilated by Homo sapiens?” And were there “random population fluctuations? Technocultural disequilibrium?”
Palaeoclimate and palaeoecology are of significant interest in relation to the “last glaciation and extreme climate fluctuations.”
They noted, however, that “while Neanderthals have disappeared as a biological species, they still live on in the form of introgressed DNA in the human gene pool, testifying to close encounters between the two species.”

Sequencing ancient DNA, including genome sequences, has revolutionized the way we understand extinct species.
This was highlighted at the close of the talk. Referring to Neanderthals, they noted: “they are still around: humans with out-of-Africa ancestry have 1-4% Neanderthal alleles and 0.1-11% Denisovan alleles; approximately 20% of the total Neanderthal genome is still preserved in out-of-Africa humans.”
These proportions, they added, appear to be stable.

The closing keynote lecture was by Professor Carlos M. Herrera from Estación Biológica de Doñana, Spanish National Research Council (CSIC).
The title to his presentation, “Wild bees from a Mediterranean sky island: diversity, trends, and thermal biology,” at once indicated that there would be a solid natural history offering incorporating fieldwork data, fundamental ecological concepts, and more.

He discussed “sky islands,” isolated mountains surrounded by different lowland environments being glacial refuges, speciation hotspots, and biogeographical singularities; the main ones in the Baetic mountain ranges being Cazorla-Segura, Sierra Nevada, and Baza-Filabres.

He noted that “isolation, historical singularity, and contrasting climate relative to surroundings, combine to turn sky islands into natural laboratories well suited for examining the ecological effects of climate change and identifying mechanisms.”

Cazorla-Segura, a species-rich community of approximately 400 wild bee species, where he has worked for three decades, possesses “elevational, geological, ecological, and climatic distinctiveness, and it represents a major biodiversity hotspot in the western Palaearctic context.”

Carlos explained that “bees are key pollinators of the regional plant community,” and described some of his findings, including that “in accordance with body shrinking expectations from climate warming models, mean body mass of individual species declined significantly over the last few decades; size reduction being strongest among large-bodied species.”
We had heard about the impacts of climate change on species and environments in several of the presentations during the conference.
Carlos’ work adds to these concerns.

“Taken together,” he explained, “climate-related changes in diversity, species composition, size distribution, and thermal features of the bee community are expected to have manifold, complex consequences for the pollination, mating systems, and population survival of the unique assemblages of bee-pollinated plants endemic to the study region.”

Following the final talk, I asked Geraldine to officially close the Calpe Conference. She thanked everyone involved with the conference: the Vice-Chancellor of the university, Professor Catherine Bachleda; university staff members; the conference team, sound technicians, and caterers as well as the Bistro Point restaurant staff, conference chair, speakers, and audience.
The conference had been a great success.

As I was putting away my notes, pens etc. in my case before leaving, I re-read the draft press release for the conference that noted: “Since Darwin’s work on the Galapagos, islands have been seen as natural laboratories for the study of evolution. The Atlantic Island archipelagoes of the Azores, Madeira, Selvagens, Canaries and Cape Verde (collectively known as Macaronesia) have received less attention but a growing body of research is bringing their significance to the fore.”

The audience had experienced some of that research over the three days. I also thought that the ecologists among us in the conference would have identified aspects of the work, including hypotheses and theories, of the giants of island biogeography; from Charles Darwin and Alfred Russel Wallace to Robert MacArthur, Edward Wilson, and others.

Dr Alex Menez is the Senior Scientific and Conservation Officer at the Gibraltar National Museum and has published several papers on natural history in Gibraltar.